Legion II. ACANTHARIA, (continued 2)

Definition.—Astrolonchida with numerous simple apophyses (four to eight or more on each radial spine), which are arranged in two opposite longitudinal rows (rarely in six such rows, opposite in three parallel planes).

The genus Astrolonche differs from the preceding Phractacanthida in the multiplication of the simple apophyses. Commonly these are opposite in pairs in two longitudinal rows (on the two edges of the compressed spine, at least two on each side). But sometimes (in the subgenus Astrolonchidium) there are six instead of two longitudinal rows of teeth, and these are placed in three parallel planes.

Subgenus 1. Astroloncharium, Haeckel.

Definition.—Each spine with two longitudinal rows of apophyses, opposite in one meridian plane.

1. Astrolonche bicruciata, n. sp.

Spines compressed, two-edged, almost of equal breadth throughout their whole length, with simple apex and small leaf-cross at the base. From the two edges of the middle part of each spine arise two pairs of opposite apophyses, which are compressed and a little curved (convex on the distal, concave on the proximal margin). All four apophyses are of the same size and form; the radial distance of each pair much smaller than their common distance from the centre.

Dimensions.—Length of the spines 0.25, breadth 0.02.

Habitat.—Central Pacific, Station 270, surface.

2. Astrolonche mucronata, Haeckel.

Acanthometra mucronata, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 49, Taf. x. fig. 9.

Aspidomma mucronatum, Haeckel, 1862, Monogr. d. Radiol., p. 424.

Spines conical, little compressed, with simple apex and small leaf-cross at the base. From the basal half of each spine arise two pairs of opposite apophyses, which exhibit a very different form. The upper or distal apophyses (nearly in the middle of the spine) are flat, leaf-shaped, broadened in the periphery, often lobed, and sometimes branched or even fenestrated. (Transition to Phractaspis and Dorataspis, or to Phractopelta?) The lower or proximal apophyses are thick, simple, all slightly curved; they are equidistant from the former and from the centre.

Dimensions.—Length of the spines 0.2 to 0.3, greatest breadth 0.01.

Habitat.—Mediterranean (Cette on the French shore), surface, J. Müller.

3. Astrolonche pectinata, Haeckel.

Acanthometra pectinata, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 48, Taf. x. figs. 1, 2.

Xiphacantha pectinata, Haeckel, 1862, Monogr. d. Radiol., p. 386.

Spines compressed quadrangular, with short, simple or bifid apex, pyramidal on the base, without leaf-cross. From the two broader edges of the proximal half arise two longitudinal rows of opposite apophyses; three to four slender teeth in each row.

Dimensions.—Length of the spines 0.2, breadth 0.08.

Habitat.—Mediterranean, Cette (French shore), surface, J. Müller.

4. Astrolonche pinnata, n. sp.

Spines in the distal half compressed, linear, two-edged, with bifid apex; in the proximal half three times as broad lanceolate, at the base pyramidal, without leaf-cross. From the two broader edges of the proximal half arise two longitudinal rows of opposite apophyses; four to six broad triangular teeth in each row.

Dimensions.—Length of the spines 0.3 to 0.4, breadth in the outer half 0.012, in the inner half 0.03 to 0.04.

Habitat.—South Atlantic, Station 332, surface.

Subgenus 2. Astrolonchidium, Haeckel.

Definition.—Each spine with three parallel double rows of opposite apophyses.

5. Astrolonche serrata, Haeckel.

Xiphacantha serrata, Haeckel, 1862, Monogr. d. Radiol., p. 386, Taf. xvii. fig. 3, Taf. xviii. figs. 14a, 14b.

Xiphacantha serrata, R. Hertwig, 1879, Organismus d. Radiol., p. 11, Taf. ii. fig. 4.

Acanthometra serrata, Haeckel, 1860, Monogr. d. Radiol., p. 807.

Spines in the distal half thin, nearly cylindrical or a little compressed, thinned towards the short simple or bifid apex; in the proximal half three to six times as broad, four-winged, with six longitudinal rows of opposite apophyses. From the edges of the two broader (lateral) wings arise three to four pairs of strong conical teeth; from the edges of the two smaller (sagittal) wings arise also three to four pairs of teeth, but very short and broad, triangular; each of these teeth bears on both its (lateral) sides two opposite slender conical teeth, which are parallel to the large conical teeth of the lateral wings. Therefore all teeth (eighteen to twenty-four) are placed opposite in pairs in three parallel planes. Base of the spines pyramidal, with a small leaf-cross. The central capsule of this large and very remarkable species commonly entirely includes the apophyses of the spines, and is opaque, whitish.

Dimensions.—Length of the spines 0.2 to 0.3, breadth of the distal half 0.002 to 0.004, of the proximal half 0.01 to 0.02.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific, surface.

Subfamily 3. Stauracanthida, Haeckel.

Definition.—Astrolonchida with a cross of four free apophyses (or four crossed longitudinal rows of apophyses) on each radial spine.

Genus 330. Xiphacantha,^[370] Haeckel, 1862, Monogr. d. Radiol., p. 384.

Definition.—Astrolonchida with four simple apophyses on each radial spine, opposite in pairs in the form of a cross.

The genus Xiphacantha was founded by me in 1862 for all those Acanthometrida which bear simple or branched apophyses on their twenty equal spines. I restrict here the genus to those Astrolonchida which bear on each spine a cross of four simple, not branched, apophyses. These are either conical teeth or broad wings, sometimes extremely thin leaves. Xiphacantha may be regarded as the ancestral form not only of the subfamily Stauracanthida, but also of the Tessaraspida, derived from the latter.

Subgenus 1. Xiphacanthonia, Haeckel.

Definition.—Apophyses of the radial spines small, formed like a tooth or a hook, not wing-shaped. Edges of the spines commonly narrow, little prominent.

1. Xiphacantha quadridentata, Haeckel.

Xiphacantha quadridentata, Haeckel, 1862, Monogr. d. Radiol., p. 387, Taf. xviii. figs. 15a, 15b.

Acanthometra quadridentata, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 48, Taf. x. fig. 3.

Spines slender, four-sided prismatic, gradually thinner towards the simple pyramidal apex. Base with large wing-cross. Four apophyses about in the middle of each spine, conical, straight, smooth, about as long as the basal breadth of the spine. Central capsule opaque, reddish-brown.

Dimensions.—Length of the spines 0.2 to 0.3, breadth in the middle part 0.012, on the base 0.02; length of the apophyses 0.02 to 0.03.

Habitat.—Mediterranean, Atlantic, Stations 348, 354, surface.

2. Xiphacantha crucifera, n. sp.

Spines slender, four-sided prismatic, thin, of nearly equal breadth throughout the whole length. Base with small wing-cross. Four apophyses much nearer the proximal than the distal end, thin, straight smooth, three to six times as long as the basal breadth of the spine. Central capsule pellucid, with yellow bodies.

Dimensions.—Length of the spines 0.4 to 0.5, breadth 0.002 to 0.004; length of the apophyses 0.01 to 0.02.

Habitat.—Central Pacific, Station 266, surface.

3. Xiphacantha spinulosa, Haeckel.

Xiphacantha spinulosa, Haeckel, 1862, Monogr. d. Radiol., p. 388, Taf. xvii. fig. 4.

Acanthometra spinulosa, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 807.

Spines stout, four-sided prismatic, of nearly equal breadth throughout the whole length, on the distal apex truncated, two-edged. Base with large wing-cross. Four apophyses about in the middle of each spine, conical, straight, spinulated, twice to four times as long as the basal breadth of the spine. Central capsule opaque, yellow.

Dimensions.—Length of the spines 0.27, breadth 0.014; length of the apophyses 0.05.

Habitat.—Mediterranean (Messina), surface.

4. Xiphacantha emarginata, n. sp.

Spines stout, four-sided, in the proximal half prismatic, in the distal half pyramidal, with emarginated apex. Base with very large wing-cross. Four apophyses about in the middle of each spine, compressed, straight, two-edged, with emarginated ends, about twice as long as the basal breadth of the spine. Central capsule small, pellucid.

Dimensions.—Length of the spines 0.2 to 0.3, breadth 0.02 to 0.03; length of the apophyses 0.04 to 0.06.

Habitat.—South Pacific, Station 291, surface.

5. Xiphacantha falcata, n. sp.

Spines slender, four-sided prismatic, gradually thickened from both ends towards the middle part, with simple apex. Base with very small wing-cross. Four apophyses about in the middle part of each spine, falcated, compressed, recurved, twice to three times as long as the greatest breadth of the spine.

Dimensions.—Length of the spines 0.3 to 0.4, greatest breadth 0.015; length of the apophyses 0.03 to 0.05.

Habitat.—Central Pacific, Station 270, surface.

6. Xiphacantha ancorata, n. sp.

Spines slender, four-sided prismatic, gradually thickened from the narrow base towards the short, simple, pyramidal apex. Base with large wing-cross. Four apophyses on the distal end, immediately below the pyramidal apex, falcated, strongly recurved, like an anchor with four strong teeth.

Dimensions.—Length of the spines 0.4 to 0.5, basal breadth 0.005, distal breadth 0.015; length of the apophyses 0.04.

Habitat.—Indian Ocean, Madagascar, Rabbe.

Subgenus 2. Xiphacanthidium, Haeckel.

Definition.—Apophyses of the radial spines broad, compressed, wing-shaped, formed like a large thin plate. Edges of the spines commonly broad, strongly prominent.

7. Xiphacantha stauroptera, n. sp.

Spines four-winged, from the middle part little thinner towards both ends. Apex simple pyramidal. Base with small wing-cross. Four apophyses wing-shaped, isosceles triangular or truncated quadrangular; their base is about half as broad as their length, and occupies in the basal half of each spine about one-sixth to one-eighth of its length.

Dimensions.—Length of the spines 0.1 to 0.15; greatest breadth (diagonal of the cross of the apophyses) 0.006 to 0.009.

Habitat.—South Atlantic, Station 332, surface.

8. Xiphacantha trigonoptera, n. sp.

Spines four-winged, tapering rapidly from the broad middle part towards both ends. Apex simple pyramidal. Base with a small wing-cross. Four apophyses equilateral triangular; their base occupies the middle of each spine, extending to about one-fifth of its length.

Dimensions.—Length of the spines 0.15 to 0.2, greatest breadth (diagonal of the cross of the apophyses) 0.06 to 0.08.

Habitat.—Central Pacific, Station 272, surface.

9. Xiphacantha macroptera, n. sp.

Spines four-winged, from the broad middle part gradually thinner towards both ends. Apex simple pyramidal. Base with small wing-cross. Four apophyses wing-shaped, very long and broad, triangular; their base occupies about the middle third of each spine; the proximal side of each wing is the shortest, truncated or concave.

Dimensions.—Length of the spines 0.4 to 0.5, greatest breadth (diagonal of the middle leaf-cross) 0.08 to 0.12.

Habitat.—North Pacific, Stations 253 to 256, surface.

10. Xiphacantha platyptera, n. sp.

Spines four-winged, nearly prismatic in the basal and distal parts. Apex truncated. Base with small wing-cross. Four apophyses wing-shaped, very broad and thin, extremely delicate, of irregular quadrangular or nearly rhomboidal form; their base occupies the middle half of the length of the spines (second and third quarter). Very variable in form. Often the edges of the wing-apophyses of the neighbouring spines seem to meet.

Dimensions.—Length of the spines 0.2 to 0.3, greatest breadth (diagonal of the leaf-cross) 0.06 to 0.08.

Habitat.—Pacific, widely distributed, Stations 239, 253, 272, 288, &c., surface.

11. Xiphacantha ciliata, n. sp. (Pl. 129, figs. 4, 5).

Spines four-winged, prismatic in the basal and the distal third. Apex pyramidal, short. Base with large leaf-cross. Four apophyses wing-shaped, nearly semicircular, with dentated edges and rough spinulate or porous faces; their base occupies the middle third of the length of each spine.

Dimensions.—Length of the spines 0.2 to 0.3, greatest breadth (diagonal of the apophysial cross) 0.08 to 0.12.

Habitat.—Tropical Atlantic, Stations 342 to 352, surface.

12. Xiphacantha alata, Haeckel.

Xiphacantha alata, Haeckel, 1862, Monogr. d. Radiol., p. 388.

Acanthometra alata, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 48, Taf. ix. figs. 1-3.

Spines four-winged, prismatic in the basal quarter, more slender in the distal half. Apex simple pyramidal. Base with small wing-cross. Four apophyses wing-shaped, nearly semicircular, with denticulated edges (and often also with spinulate faces); their base occupies the second quarter of the length of each spine.

Dimensions.—Length of the spines 0.3 to 0.4, greatest breadth (diagonal of the apophysial cross) 0.05 to 0.06.

Habitat.—Mediterranean (Nice), Müller, (Portofino), Haeckel.

Genus 331. Stauracantha,^[371] Haeckel, 1881, Prodromus, p. 465.

Definition.—Astrolonchida with four branched (but not latticed) apophyses on each radial spine, opposite in pairs in the form of a cross.

The genus Stauracantha differs from its ancestral form, Xiphacantha, in the ramification of the four crossed apophyses on each spine. These bear either lateral branches, which are parallel to the cross axes of the radial spine itself (subgenus Stauracanthonium), or they are forked, with divergent branches not parallel to those cross axes (subgenus Stauracanthidium). Both subgenera may perhaps be better separated as genera. They form the transition to the Stauraspida.

Subgenus 1. Stauracanthonium, Haeckel.

Definition.—Apophyses of the radial spines not forked, but crossed by perpendicular branches, which are placed in tangential planes and parallel to the cross axes of the quadrangular spine itself.

1. Stauracantha orthostaura, n. sp. (Pl. 130, fig. 5).

Spines four-sided prismatic, with simple apex and small leaf-cross at the base; with four thin slender conical apophyses in the proximal third. Each apophysis represents a regular rectangular cross, being intersected in its middle by one perpendicular rod of its own length.

Dimensions.—Length of the spines 0.3, breadth 0.02; distance of the apophyses from the apex 0.15 to 0.2.

Habitat.—South Pacific, Station 169, surface.

2. Stauracantha tetrastaura, n. sp.

Spine four-winged prismatic, with four broad prominent edges, pyramidal apex, and large basal leaf-cross, with four broad compressed apophyses about in the middle. Each apophysis represents a vertical lamella (placed in a meridian) with convex distal and concave proximal edge, and is crossed in its apical part by one perpendicular short rod.

Dimensions.—Length of the spines 0.5, breadth 0.03; distance of the apophyses from the centre 0.2.

Habitat.—Central Pacific, Station 272, surface.

3. Stauracantha diplostaura, n. sp.

Spines four-sided prismatic, with truncated apex and broad basal leaf-cross; in the proximal half with four slender conical apophyses. Each apophysis is crossed in its apical half at right angles by two short parallel transverse rods.

Dimensions.—Length of the spines 0.32, breadth 0.012; distance of the apophyses from the centre 0.11.

Habitat.—South Pacific, Station 291, surface.

4. Stauracantha scalaris, n. sp.

Spines four-winged prismatic, with four broad prominent edges, truncated apex, and small basal leaf-cross; in the proximal third with four compressed lamellar apophyses. Each apophysis is pinnate with opposite pinnulæ, or crossed at right angles by three to six parallel transverse rods.

Dimensions.—Length of the spines 0.24, breadth 0.016; central distance of the apophyses 0.12.

Habitat.—Indian Ocean (Madagascar), Rabbe, surface.

5. Stauracantha johannis, n. sp. (Pl. 132, fig. 11).

Spines four-sided pyramidal, with simple apex and broad basal leaf-cross, with four large conical apophyses about in their middle. Each apophysis bears two irregular rows of alternating perpendicular lateral branches, the length of which decreases from the base towards the apex of the apophysis.

Dimensions.—Length of the spines 0.2, middle breadth 0.02; central distance of the apophyses 0.1.

Habitat.—South-east Pacific (off Juan Fernandez), Station 300, surface.

6. Stauracantha murrayana, Haeckel.

Xiphacantha species, Wyville Thomson, 1877, The Atlantic, vol. i. p. 235, fig. 53.

Xiphacantha murrayana, Haeckel, 1878, Protistenreich, p. 45, fig. 33.

Spines quadrangular prismatic, with pyramidal apex and small basal leaf-cross, with four regular conical apophyses in the proximal part. Each apophysis is crossed at right angles by two parallel transverse rods; the smaller apical rod is simple; the larger basal rod is crossed again on each side by a secondary perpendicular branch, which therefore is parallel to the apophysis itself.

Dimensions.—Length of the spines 0.3, breadth 0.01, distance of the apophyses 0.08.

Habitat.—South Atlantic, Station 332, surface.

7. Stauracantha pinnulata, n. sp.

Spines four-winged pyramidal, with prominent edges, simple apex and large basal leaf-cross, in the middle with doubly pinnate triangular apophyses. Each apophysis is crossed at right angles by three to four transverse parallel rods, which bear again perpendicular secondary branches; the outline of the doubly pinnate apophysis is an isosceles triangle.

Dimensions.—Length of the spines 0.3, middle breadth 0.02; distance of the apophyses 0.12.

Habitat.—North Pacific, Station 244, surface.

Subgenus 2. Stauracanthidium, Haeckel.

Definition.—Apophyses of the radial spines forked, each with two divergent terminal branches, which are not parallel to the cross axes of the quadrangular spine.

8. Stauracantha stauraspis, Haeckel.

Dorataspis polyancistra, juvenis, Haeckel, 1862, Monogr. d. Radiol., p. 418, Taf. xxi. fig. 7.

Spines slender, quadrangular prismatic, with simple apex and pyramidal base (without basal leaf-cross); with four slender apophyses, which are simply forked in the outer third. Each apophysis with two recurved fork branches.

Dimensions.—Length of the spines 0.12, breadth 0.004; distance of the apophyses 0.06.

Habitat.—Mediterranean (Messina), surface.

9. Stauracantha bifurca, n. sp.

Spines stout, four-winged prismatic, with pyramidal apex and pyramidal base (without leaf-cross); in their middle with four compressed, little curved apophyses (convex on the outer, concave on the inner edge), which are simply forked at the end. Each apophysis with two short straight fork branches.

Dimensions.—Length of the spines 0.2, breadth 0.006; distance of the apophyses 0.08.

Habitat.—Central Pacific, Station 266, surface.

10. Stauracantha quadrifurca, n. sp. (Pl. 130, fig. 4).

Spines slender, four-sided prismatic, with simple apex and pyramidal base (without leaf-cross); with four slender apophyses, which are doubly forked about in their middle. Each apophysis with four short and thin terminal branches.

Dimensions.—Length of the spines 0.2, breadth 0.002; distance of the apophyses from the centre 0.08.

Habitat.—South Atlantic, Stations 325 to 330, surface.

Genus 332. Phatnacantha,^[372] Haeckel, 1881, Prodromus, p. 465.

Definition.—Astrolonchida with four apophyses on each radial spine, opposite in pairs in cross form, and forming a lattice-plate by communicating branches.

The genus Phatnacantha has been derived from the preceding Stauracantha by concrescence of the branches of the apophyses. Therefore each spine bears a lattice-plate or a fenestrated shield. If the growing plates of the neighbouring spines meet together, then the characteristic lattice-shell of the Tessaraspida is perfect. Either each plate bears four crossed pores (like Tessaraspis), or a larger number of pores (four aspinal and four to eight or more coronal) like Icosaspis.

1. Phatnacantha tessaraspis, n. sp.

Spines quadrangular prismatic, with simple pyramidal apex and small basal leaf-cross. Each spine bears in the basal half a square plate, which is perforated by four square pores; margin of the plate with twelve short straight teeth.

Dimensions.—Length of the spines 0.12, breadth 0.005.

Habitat.—Central Pacific, Station 265, surface.

2. Phatnacantha icosaspis, n. sp. (Pl. 130, fig. 6).

Spines quadrangular with prominent edges; prismatic in the basal half, with a broad basal leaf-cross, pyramidal in the distal half, with a simple or truncate apex. Each spine bears in the middle part a square plate, which is perforated by eight to sixteen or more square pores (four aspinal and four to eight or more coronal); margin of the plate with twenty-four to forty-eight or more short straight irregular compressed teeth.

Dimensions.—Length of the spines 0.18, breadth 0.008.

Habitat.—Central Pacific, Station 273, surface.

Genus 333. Pristacantha,^[373] n. gen.

Definition.—Astrolonchida with numerous simple apophyses (eight to sixteen or more on each radial spine) which are arranged in four longitudinal rows opposite in pairs in the form of a cross.

The genus Pristacantha differs from all other Stauracanthida in the multiplication of the crossed apophyses (at least eight on each spine), and exhibits therefore to them the same relation as Astrolonche exhibits to the other Phractacanthida. The remarkable Astrolonchidium serratum appears intermediate between both groups.

1. Pristacantha octodon, n. sp. (Pl. 130, fig. 9).

Spines four-sided prismatic, a little broader in the middle part than at either end, with thin prominent edges. Apex truncate or pyramidal. Base pyramidal, with a small leaf-cross. From the four edges arise in the basal half (between first and second third of the length) eight slender, conical, or triangular apophyses (two on each edge).

Dimensions.—Length of the spines 0.4 to 0.6, breadth 0.02 to 0.04.

Habitat.—Central Pacific, Station 271, surface.

2. Pristacantha dodecodon, n. sp. (Pl. 130, fig. 8).

Spines four-winged, of lanceolate outline, tapering from the broader middle towards the two ends. Apex pyramidal. Base with a large leaf-cross. From the four wings arise in the basal part (between first and second third of the length) twelve triangular apophyses (three from each wing).

Dimensions.—Length of the spines 0.3, breadth in the middle 0.03.

Habitat.—North Pacific, Station 244, surface.

3. Pristacantha polyodon, n. sp. (Pl. 130, fig. 7).

Spines in the distal half four-sided prismatic, thin, with pyramidal apex; in the basal half much broader, four-winged, with a large leaf-cross on the base. From the four wings of the basal half arises a variable number of slender teeth or triangular apophyses, commonly sixteen to twenty-four, often irregular (four to six from each wing).

Dimensions.—Length of the spines 0.3 to 0.4, breadth in the distal part 0.007 to 0.01, in the basal part 0.02 to 0.03.

Habitat.—South Pacific (off New Zealand), Station 169, surface.

Family XXXVII. Quadrilonchida, Haeckel (Pl. 131).

Acanthostaurida, Haeckel, 1881, Prodromus, p. 466.

Definition.—Acantharia with twenty radial spines of very unequal size, disposed according to the law of the Icosacantha; four equatorial spines much larger than the sixteen others. No lattice-shell.

The family Quadrilonchida differs from the foregoing ancestral family, the Astrolonchida, in the unequal development of the twenty radial spines. The four equatorial spines are constantly much larger, and often also of another form and shape, than the sixteen other spines; often also among these the eight tropical spines are larger and of another form than the eight polar spines. Therefore the five parallel girdles or zones of every four spines, which in the Astrolonchida are equal, are here distinctly unequal. The whole body is flattened and compressed in the direction of the spineless axis, so that the equatorial plane is larger than any other plane, laid through the centre. In consequence of this flattening the central capsule is also commonly compressed and flattened, lenticular or discoidal, rarely spherical. In the Astrolonchida the "promorph" or the "geometrical fundamental form" is constantly a square double pyramid, the axes of which are of equal length. In the Quadrilonchida it becomes a square double pyramid, the two equatorial axes of which (or the diagonals of the square) are constantly longer than all other axes.

In the simpler forms of Quadrilonchida are found only two different kinds of spines, the four larger equatorial spines being of the same size and form, and the sixteen smaller spines also not differing from one another (Acanthostaurus, &c.). But in the majority of this family there are three different kinds: four larger equatorial spines, eight tropical spines of middle size, and eight smaller polar spines (Belonostaurus, &c.); the latter become sometimes rudimentary, so that only twelve spines are developed (four larger equatorial and eight smaller tropical spines). In this case the development of the flat discoidal body is much stronger in the equatorial plane than in all other planes. These discoidal or lenticular Quadrilonchida exhibit a relation to the spherical Astrolonchida similar to that which the Discoidea exhibit to the Sphæroidea among the Sphærellaria.

A further morphological differentation takes place in the remarkable genera Lonchostaurus and Zygostaurus. In the former (Pl. 131, figs. 4-6) the four larger equatorial spines becomes differentiated in pairs, so that the opposite equal spines of one pair, c1, c3 (in the longitudinal or hydrotomical axis), are larger, and often also of another form, than the opposite equal spines of the other pair, c2, c4 (in the transverse or geotomical axis). The most peculiar form is the rather common Zygostaurus (Pl. 131, figs. 7, 8). Here the two opposite spines of one equatorial axis (of the longitudinal axis) become very different, so that the anterior or frontal spine (c1) is very unequal to the posterior or caudal spine (c3), whereas the two opposite spines, of the other equatorial axis (of the transverse axis) remain equal (c2, c4). Therefore the fundamental forms become here "amphithect," as in the Ctenophora.

The numerous Quadrilonchida may be disposed in two different subfamilies: in the Acanthostaurida all twenty radial spines are simple, without apophyses; in the Lithopterida all twenty spines (or only one part of them) bear two opposite apophyses (or lateral transverse processes). The former correspond to the Zygacanthida, the latter to the Phractacanthida among the Astrolonchida. The two opposite apophyses are simple in Quadrilonche (Pl. 133, fig. 1). In Xiphoptera they are provided on their distal side with lateral branches which are parallel to the spine itself. In Lithoptera the spines bear two to four parallel pairs of transverse apophyses, and these are crossed by perpendicular branches, parallel to the spine itself, so that there arise fenestrated wings or latticed plates, comparable to the sails of a wind-mill. The lattice-work of these plates lies in the same meridian plane with the radial spine itself, and is therefore not comparable to the fenestrated apophyses of Doracantha, of Phatnacantha, and of the Dorataspida; in these the lattice-plates lie in tangential planes, perpendicular to the radial spine.

The apophyses of the Lithopterida may be developed either on all twenty spines equally, or only on twelve spines (four equatorial and eight tropical, whilst the eight polar spines are simple, Pl. 131, fig. 10), or only on the four equatorial spines (whilst the sixteen others are simple, Pl. 131, fig. 9).

The Central Capsule of the Quadrilonchida is rarely spherical, commonly more or less compressed from both poles of the spineless axis, lenticular or discoidal, sometimes square. It is enveloped by a voluminous calymma constantly bearing coronals of "Myophrisca" (compare p. 724).

Synopsis of the Genera of Quadrilonchida.

II. Subfamily Acanthostaurida. All twenty spines simple, without lateral apophyses (sometimes forked, but neither branched nor latticed). Four equatorial spines of equal size and form. Eight tropical and eight polar spines nearly equal, 334. Acanthostaurus.

Eight tropical and eight polar spines very different, 335. Belonostaurus.

Four equatorial spines of very different size or form (the two lateral constantly equal). Two principal spines of equal size and form, 336. Lonchostaurus.

Two principal spines (frontal and caudal) very different, 337. Zyostaurus.

II. Subfamily Lithopterida. Either all twenty spines or a part of them provided with two opposite lateral branches or apophyses. Apophyses simple, neither branched nor latticed, 338. Quadrilonche.

Apophyses branched or pinnate, but not latticed, 339. Xiphoptera.

Apophyses latticed, with fenestrated network, 340. Lithoptera.

I. Subfamily Acanthostaurida. All twenty spines simple, without lateral apophyses (sometimes forked, but neither branched nor latticed).

Four equatorial spines of equal size and form.

Eight tropical and eight polar spines nearly equal,

34. Acanthostaurus.

Eight tropical and eight polar spines very different,

35. Belonostaurus.

Four equatorial spines of very different size or form (the two lateral constantly equal).

Two principal spines of equal size and form,

336. Lonchostaurus.

Two principal spines (frontal and caudal) very different,

337. Zyostaurus.

II. Subfamily Lithopterida. Either all twenty spines or a part of them provided with two opposite lateral branches or apophyses.

Apophyses simple, neither branched nor latticed,

338. Quadrilonche.

Apophyses branched or pinnate, but not latticed,

339. Xiphoptera.

Apophyses latticed, with fenestrated network,

340. Lithoptera.

Subfamily 1. Acasthostaurida, Haeckel, 1881, Prodromus, p. 466.

Definition.—Quadrilonchida with simple radial spines, without apophyses.

Genus 334. Acanthostaurus,^[374] Haeckel, 1862, Monogr. d. Radiol., p. 395.

Definition.—Quadrilonchida with four equatorial spines of equal size and form, which are much larger than the sixteen other spines. Eight tropical and eight polar spines nearly equal. No apophyses.

The genus Acanthostaurus is the most simple and primitive form of the Quadrilonchida, and the common ancestral genus of this family; it is at the same time its most common and widely distributed form. Some species appear in astonishing numbers in different seas. It has been derived from Acanthometron by stronger development of the four equatorial spines, which are all of equal size and much larger than the sixteen others.

Subgenus 1. Acostaurus, Haeckel.

Definition.—All twenty spines separated, in the centre united only by the triangular faces or the meeting leaf-shaped edges of their pyramidal bases.

1. Acanthostaurus aequatorialis, n. sp.

Spines cylindrical, of nearly equal breadth throughout their whole length. Apex simple conical. Base with a large leaf-cross. Four equatorial spines of the same form as the sixteen others, but much longer and about three times as broad.

Dimensions.—Length of the four major spines 0.2 to 0.25, breadth 0.008; length of the sixteen minor spines 0.01 to 0.15, breadth 0.003.

Habitat.—Equatorial Pacific, Station 271, surface.

2. Acanthostaurus bipennis, n. sp.

Spines linear, sword-shaped, strongly compressed, two edged; of nearly equal breadth in their whole length. Apex bifid. Base with a small leaf-cross. Four equatorial spines of the same form as the sixteen others, but twice as long and as broad.

Dimensions.—Length of the four major spines 0.4 to 0.5, of the sixteen minor 0.2 to 0.3; breadth of the former 0.02, of the latter 0.01.

Habitat.—North Pacific, Station 244, surface.

3. Acanthostaurus conacanthus, n. sp.

Spines conical, short, gradually tapering from the thick base towards the simple apex. Base with large leaf-cross. Four equatorial spines more cylindrical, twice to three times as long and as broad as the sixteen others.

Dimensions.—Length of the four major spines 0.15 to 0.2, of the sixteen minor 0.05 to 0.08; basal breadth of the former 0.03, of the latter 0.012.

Habitat.—South Atlantic, Station 332, surface.

4. Acanthostaurus purpurascens, Haeckel.

Acanthostaurus purpurascens, Haeckel, 1862, Monogr. d. Radiol., p. 395, Taf. xix. figs. 1, 2.

Acanthostaurus purpurascens, R. Hertwig, 1879, Organism. d. Radiol., Taf. i. figs. 8, 9, Taf. iii. figs. 13, 15.

Acanthometra purpurascens, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 809.

Spines nearly cylindrical, with four blunt (often scarcely visible) edges, tapering slightly from the central to the distal end. Apex bifid, with two short parallel teeth. Base with a broad leaf-cross. Four equatorial spines one and a half times to twice as long and broad as the sixteen others. Central capsule cruciate, with four arms (enveloping the basal part of the four large spines); filled up with yellow bodies and purple granules. Calymma large, with a network of purple granules. The four main spines are constantly much larger than the sixteen others, but in variable proportion. The eight polar spines are sometimes rudimentary.

Dimensions.—Length of the four major spines 0.3 to 0.4, of the sixteen minor 0.15 to 0.3; breadth of the former 0.012, of the later 0.008 or less.

Habitat.—Mediterranean (Messina); Atlantic, Stations 348 to 354, surface.

5. Acanthostaurus pallidus, Haeckel.

Acanthostaurus pallidus, Haeckel, 1862, Monogr. d. Radiol., p. 396.

Acanthometra pallida, Claparède et Lachmann, 1858, Études sur les Infusoires, &c., p. 461, Taf. xxiv. fig. 6.

Spines four-sided prismatic, with four blunt edges, of nearly equal breadth throughout their whole length. Apex bifid. Base with a small leaf-cross. Four equatorial spines much larger than the sixteen others. Central capsule spherical, transparent, containing some yellow bodies.

Dimensions.—Length of the four main spines 0.12 to 0.2, of the sixteen others 0.04 to 0.08; breadth of the former 0.01, of the latter 0.004.

Habitat.—North Atlantic, west coast of Norway, Claparède; Færöe Channel, John Murray.

6. Acanthostaurus forceps, Haeckel.

Acanthostaurus forceps, Haeckel, 1862, Monogr. d. Radiol., p. 396, Taf. xix. figs. 3, 4.

Acanthometra forceps, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 809.

Spines pincer-shaped, linear, compressed, cleft nearly throughout their whole length into two parallel thin, straight branches, which are united only at the pyramidal base and by means of a small bridge in the middle part. Four main spines twice as long and as broad as the sixteen others. Central capsule square, filled up with red pigment, and containing yellow bodies. The diagonals of the square are the two equatorial axes.

Dimensions.—Length of the four main spines 0.1, of the sixteen others 0.05; breadth of the former 0.01, of the latter 0.005.

Habitat.—Mediterranean (Messina); North Atlantic, Canary Islands, Station 354, surface.

7. Acanthostaurus hastatus, Haeckel.

Acanthostaurus hastatus, Haeckel, 1862, Monogr. d. Radiol., p. 397, Taf. xix. fig. 5.

Acanthometra hastata, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 809.

Spines of very different size and form; four equatorial spines cylindrical in the basal half, spear-shaped or lanceolate in the distal half, with thin edges, little longer, but five to eight times as broad as the sixteen smaller spines, which are cylindrical, of equal breadth throughout their whole length, with bifid apex. Base of all twenty spines pyramidal, without leaf-cross. Central capsule yellow, spherical, or lenticular.

Dimensions.—Length of the four major spines 0.066, breadth in the middle 0.005, on the apex 0.008; length of the sixteen smaller spines 0.054, breadth 0.001.

Habitat.—Mediterranean (Messina), surface.

Subgenus 2. Staurolithium, Haeckel, 1862, Monogr. d. Radiol., p. 401.

Definition.—All twenty spines in the centre melted and grown together, forming one single, star-like piece of acanthin.

8. Acanthostaurus cruciatus, Haeckel.

Staurolithium cruciatum, Haeckel, 1862, Monogr. d. Radiol., p. 401, Taf. xx. fig. 6.

Astrolithium cruciatum, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 811.

Spines cylindrical, of equal breadth throughout their whole length. Apex simple conical. Four equatorial spines twice as long and broad as the sixteen other spines. All twenty spines in the centre melted and grown together, forming a single piece of acanthin. Central capsule spherical, red-brown, opaque.

Dimensions.—Length of the four equatorial spines 0.12, breadth 0.006; length of the sixteen smaller spines 0.06, breadth 0.003.

Habitat.—Mediterranean (Messina), surface.

Genus 335. Belonostaurus,^[375] n. gen.

Definition.—Quadrilonchida with four equatorial spines of equal size and form, which are much larger than the sixteen other spines. Eight tropical and eight polar spines very different. No apophyses.

The genus Belonostaurus differs from the preceding Acanthostaurus in the unequal size and form of the eight tropical and the eight polar spines; the latter are much smaller than the former and often quite rudimentary, so that the skeleton appears composed only of twelve spines, four larger equatorial and eight smaller tropical spines. The central bases of the polar spines are constantly preserved. The central capsule is a flattened square disk.

1. Belonostaurus quadratus, n. sp.

Four equatorial spines little compressed, almost cylindrical in the basal half, lanceolate, broader, with simple apex in the distal half. Eight tropical spines a little shorter, but only half as broad, sword-shaped, two-edged, of equal breadth, with simple apex. Eight polar spines very short, conical, also with simple apex. Base without leaf-cross, a simple pyramid.

Dimensions.—Length of the four equatorial spines 0.18, of the eight tropical spines 0.14, of the eight polar spines 0.04.

Habitat.—Central Pacific, Station 271, surface.

2. Belonostaurus bicuspis, n. sp.

Four equatorial spines compressed, almost lanceolate in the basal half, bifid, with two large, bent, little divergent horns in the distal half. Eight tropical spines nearly of the same form, but only half as large, with much smaller horns. Eight polar spines rudimentary, very short, conical, with simple apex. Base with a large leaf-cross.

Dimensions.—Length of the four equatorial spines 0.2, of the eight tropical spines 0.1, of the eight polar spines 0.02.

Habitat.—Central Pacific, Station 263, surface.

Genus 336. Lonchostaurus,^[376] Haeckel, 1862, Monogr. d. Radiol., p. 397 (sensu emendato).

Definition.—Quadrilonchida with four equatorial spines of unequal size and form; the principal spines (in the longitudinal axis) larger than the lateral spines (in the transverse axis); both opposite spines of each pair equal. Sixteen other spines much smaller (often the eight tropical larger than the eight rudimentary polar spines). No apophyses.

The genus Lonchostaurus differs from the two preceding genera in the unequal size and shape of both equatorial pairs of spines, whilst the two opposite spines of each pair are equal. Therefore the equatorial plane is here a rhombus, not a square, as in the preceding genera. We encounter here for the first time the differentiation of the two equatorial axes, the longitudinal (or hydrotomical) and the transverse (or geotomical) axis. The sixteen other spines are constantly smaller (often also the eight polar more or less rudimentary).

1. Lonchostaurus rhomboides, n. sp. (Pl. 131, fig. 6).

Four equatorial spines cylindrical, twice to three times as broad as the sixteen smaller spines, conical at the distal apex; the two opposite spines of the longitudinal axis twice as long as those of the transverse axis. Sixteen smaller spines conical at the base, with simple bristle-shaped apex. The surface of the rhombical calymma, including the spines, was covered in the figured specimen with small plates like those of Sphærocapsa.

Dimensions.—Length of the cross (longitudinal axis) 0.24, breadth (transverse axis) 0.12.

Habitat.—South Pacific, Station 302, depth 1450 fathoms.

2. Lonchostaurus lanceolatus, n. sp.

Four equatorial spines compressed, lanceolate, tapering equally from the middle towards the two ends; the two opposite spines of the longitudinal axis one and a half times as long as those of the transverse axis. Sixteen smaller spines compressed, linear, two-edged, half as long and only one-fourth as broad as the two longitudinal spines.

Dimensions.—Length of the equatorial cross 0.3, breadth 0.2.

Habitat.—Central Pacific, Station 272, surface.

3. Lonchostaurus bifidus, n. sp.

Four equatorial spines compressed, nearly rectangular, forked, with two long and thin, bent, little divergent horns; the two opposite spines of the longitudinal axis about one-third longer and broader than those of the transverse axis. Sixteen smaller spines of the same form, also forked, but the eight tropical only half as large, and the eight polar spines scarcely one-fourth as large as the two longitudinal spines.

Dimensions.—Length of the equatorial cross 0.36, breadth 0.26.

Habitat.—South-west Pacific, Station 166, surface.

4. Lonchostaurus bifurcus, n. sp. (Pl. 131, fig. 4).

Four equatorial spines nearly rhomboidal, about one and a half times as large as the eight tropical and three times as large as the eight polar spines; the two opposite spines of the longitudinal axis only with two large divergent straight horns; the two spines of the transverse axis somewhat shorter, with four short horns (the two outer horns longer than the two inner). Eight tropical spines doubly forked, each with four thin bristle-shaped horns. Eight polar spines very short, each with two thin bristle-shaped, much divergent horns.

Dimensions.—Length of the equatorial cross 0.34, breadth 0.28.

Habitat.—North-west Pacific, Station 236, surface.

5. Lonchostaurus rhombicus, n. sp.

Four equatorial spines nearly rhomboidal, tapering from the broader middle towards the two ends. Leaf-cross of their base very large. The two opposite spines of the longitudinal axis about one-third larger than the two spines of the transverse axis. Eight tropical spines of the same form, but only half as large. Eight polar spines rudimentary, very short, conical.

Dimensions.—Length of the equatorial cross 0.4, breadth 0.3.

Habitat.—North Pacific, Station 253, surface.

6. Lonchostaurus crystallinus, n. sp. (Pl. 131, fig. 5).

Four equatorial spines lanceolate or rhomboidal, with broad leaf-cross at the base, of a peculiar crystalline structure and a lamellated surface, both opposite spines of the longitudinal axis twice as large as the two spines of the transverse axis. Eight tropical spines of similar form, but only half as large, and with a very large, extremely prominent, lamellated leaf-cross. Eight polar spines quite rudimentary, scarcely prominent.

Dimensions.—Length 0.36, breadth 0.2.

Habitat.—Central Pacific, Station 271, surface.

Genus 337. Zygostaurus,^[377] n. gen.

Definition.—Quadrilonchida with four equatorial spines of unequal size and form; both lateral spines (in the transverse axis) equal; but both principal spines (in the longitudinal axis) very different, the frontal larger than the caudal. Sixteen other spines much smaller (often the eight tropical larger than the eight rudimentary polar spines). No apophyses.

The genus Zygostaurus differs from all other Staurolonchida in the peculiar differentiation of the four equatorial spines; the two opposite spines of the hydrotomical or longitudinal axis being very different in size and form (the frontal spine forked, the caudal spine simple); whilst the two opposite spines of the geotomical or lateral axis (perpendicular to the former) are equal, forked, but different in shape from the former. Therefore the geometrical fundamental form of the body in this remarkable genus becomes "amphithect" or "bilateral" in the widest signification of this term (comp. my General Morphology, vol. i. pp. 480, 482). Of the three different dimensive axes one (the longitudinal) exhibits unequal poles, whilst the two other (the sagittal and lateral) axes exhibit equal poles.

1. Zygostaurus amphithectus, n. sp. (Pl. 131, fig. 7).

Frontal spine (c1) little different from the two lateral spines; each with two divergent curved horns, which are equal and of about the same length as the simple broad basal part. Caudal spine (c3) simple, spindle-shaped, about as long as the frontal spine. Tropical spines little smaller than the three former, and of the same symmetrical forked form. Eight polar spines much smaller, but also forked, with thin bristle-shaped branches.

Dimensions.—Length of the cross (longitudinal axis) 0.5, breadth (lateral axis) 0.4.

Habitat.—Central Pacific, Station 272, surface.

2. Zygostaurus longicornis, n. sp.

Frontal spine (c1) little different from the two lateral spines, each with two divergent curved horns, which are equal and of about the same length as the simple broad basal part. Caudal spine (c3) simple, lanceolate, shorter than the frontal spine. Eight tropical spines in the basal part smaller than the three former, but with much longer fork-branches, which are prolonged into very thin and long bristles. Eight polar spines rudimentary, very short.

Dimensions.—Length of the equatorial cross 0.4, breadth 0.3.

Habitat.—South Pacific, Station 295, surface.

3. Zygostaurus cornutus, n. sp.

Frontal spine (c1) little different from the two lateral spines, each with two divergent straight horns, which are shorter than the basal part. Caudal spine (c3) simple, triangular, shorter than the three former. Eight tropical spines of equal size and form, doubly forked, each with four thin, bristle-shaped, little divergent teeth. Eight polar spines short, simply forked.

Dimensions.—Length of the equatorial cross 0.5, breadth 0.4.

Habitat.—Indian Ocean (Madagascar), Rabbe, surface.

4. Zygostaurus caudatus, n. sp.

Frontal spine (c1) very different from the others, pincer-shaped, with two long, nearly parallel slightly bent horns. Lateral spines (c2 and c4) only half as long, with two short, nearly parallel horns. Caudal spine (c3) very long and stout, spindle-shaped, about twice as long as the frontal spine. Eight tropical spines of equal size and form, symmetrical, with two long and thin, divergent horns. Eight polar spines short and stout, with two divergent horns.

Dimensions.—Length of the equatorial cross 0.8, breadth 0.3.

Habitat.—Central Pacific, Station 265, surface.

5. Zygostaurus frontalis, n. sp.

Frontal spine (c1) very different from the others, with two very long, divergent, stout branches. Lateral spines (c2 and c4) only half as long, each with two stout, nearly parallel horns of equal length. Caudal spine (c3) simple, sword-like, shorter than the three former. Eight tropical spines of equal size and form, symmetrical, of the same shape as the two lateral, but only half as large. Eight polar spines very small, rudimentary, each with two short teeth.

Dimensions.—Length of the equatorial cross 0.7, breadth 0.5.

Habitat.—Central Pacific, Station 274, surface.

6. Zygostaurus sagittalis, n. sp. (Pl. 131, fig. 8).

Frontal spine (c1) very different from the others, with two equal, strongly divergent, bent horns. Lateral spines (c2 and c4) little smaller, but with two very unequal horns (the anterior shorter than the posterior). Caudal spine (c3) simple, sword-like or triangular, two-edged, longer than the frontal spine. Eight tropical spines different, the four anterior (b1, b4, d1, d4) smaller, with longer horns; the four posterior (b2, b3, d2, d3) broader, with shorter horns; the anterior horn of each tropical spine is longer than the posterior. Eight polar spines rudimentary, simple, very short.

Dimensions.—Length of the equatorial spine-cross 0.6, breadth 0.4.

Habitat.—Central Pacific, Station 271, surface.

Subfamily 2. Lithopterida, Haeckel.

Definition.—Quadrilonchida with two opposite transverse apophyses either on all twenty spines or only on a part of them.

Genus 338. Quadrilonche,^[378] n. gen.

Definition.—Quadrilonchida with two simple opposite apophyses either on each radial spine or only on a part of the twenty spines.

The genus Quadrilonche is the ancestral form of the Lithopterida, or of those Quadrilonchida which bear two opposite apophyses or transverse processes. In Quadrilonche these apophyses are simple, whilst they are branched in Xiphoptera and fenestrated in Lithoptera. Each of these three genera may be divided into three subgenera; in the first only the four equatorial spines are provided with apophyses, in the second twelve spines (four equatorial and eight tropical), in the third subgenus all twenty spines.

Subgenus 1. Quadriloncharium, Haeckel.

Definition.—Four large equatorial spines provided with transverse apophyses; sixteen other smaller spines simple, without apophyses.

1. Quadrilonche tetrastaura, n. sp.

Four equatorial spines very large, compressed, two-edged, each crossed in the distal third by two opposite simple apophyses. Sixteen other spines also compressed, linear, somewhat shorter than the former and only half as broad, without apophyses.

Dimensions.—Length of the four major spines 0.12, breadth 0.02; length of the sixteen minor spines 0.08, breadth 0.01.

Habitat.—Central Pacific, Station 266, surface.

2. Quadrilonche platystaura, n. sp. (Pl. 131, fig. 2).

Four equatorial spines lanceolate, compressed, with two opposite triangular simple apophyses in the broadest middle part. Sixteen other spines also lanceolate, much smaller, of about half the length, but only of one-fourth the breadth, without apophyses.

Dimensions.—Length of the four major spines 0.2, breadth 0.018; length of the sixteen minor spines 0.1, breadth 0.004.

Habitat.—North Pacific, Station 235, surface.

Subgenus 2. Quadrilonchidium, Haeckel.

Definition.—All twenty spines provided with transverse apophyses.

3. Quadrilonche mesostaura, n. sp. (Pl. 131, fig. 1).

Four equatorial spines almost of the some form and length as the sixteen others, but of double or triple the breadth; each spine in its middle third with two opposite broad triangular apophyses, in the basal third rectangular, compressed, in the distal third isosceles triangular, with simple apex.

Dimensions.—Length of the four major spines 0.16, breadth 0.01 to 0.015; length of the sixteen minor spines 0.12, breadth 0.005.

Habitat.—Tropical Atlantic, Station 345, surface.

4. Quadrilonche telostaura, n. sp.

Four equatorial spines one and a half times as long and three times as broad as the sixteen others; all twenty spines cylindrical, of equal breadth throughout their whole length, with simple conical apex; each spine crossed in the distal third by two opposite, simple, conical apophyses.

Dimensions.—Length of the four major spines 0.3, breadth 0.012; length of the sixteen minor spines 0.2, breadth 0.004.

Habitat.—South Atlantic, Station 325, surface.

Genus 339. Xiphoptera,^[379] Haeckel, 1881, Prodromus, p. 466.

Definition.—Quadrilonchida with two opposite branched (but not latticed) apophyses, either on each radial spine or only on a part of the twenty spines.

The genus Xiphoptera differs from the preceding ancestral genus Quadrilonche in the ramification of the apophyses, which bear perpendicular branches on their distal side. These are therefore parallel to the spine itself. If the branches become united by transverse beams then we get Lithoptera.

1. Xiphoptera tessaractena, n. sp.

Four equatorial spines in the outer third crossed by two opposite transverse apophyses, each of which bears on its distal side two to three branches, perpendicular to the apophysis and parallel to the spine itself. Sixteen other spines much smaller, in the outer third crossed by two simple opposite transverse apophyses.

Dimensions.—Length of the four major spines 0.18, of the sixteen minor 0.05 to 0.1.

Habitat.—North Pacific, Station 238, surface.

2. Xiphoptera dodecactena, n. sp. (Pl. 131, fig. 3).

Four equatorial spines one and a half times to twice as long and broad as the eight tropical spines. These twelve spines have the same form and are crossed in their distal third by two large opposite transverse apophyses, each of which bears on its distal side two to four branches, perpendicular to the apophysis and parallel to the spine. Eight polar spines much smaller than the twelve others, simple, without apophyses. The central capsule of this species exhibited a conical protuberance around the base of each individual spine.

Dimensions.—Length of the twelve larger spines 0.1 to 0.2, of the eight smaller 0.02 to 0.06.

Habitat.—Central Pacific, Station 272, surface.

3. Xiphoptera icosactena, n. sp.

Four equatorial spines about twice as long and four times as broad as the sixteen other spines. All twenty spines crossed in the outer third by two large opposite transverse apophyses, each of which bears on its distal side two to four branches perpendicular to the apophysis and parallel to the spine itself.

Dimensions.—Length of the four equatorial spines 0.26, of the sixteen smaller 0.11 to 0.14.

Habitat.—South Pacific, Station 288, surface.

Genus 340. Lithoptera,^[380] J. Müller, 1858, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 155.

Definition.—Quadrilonchida with two opposite branched and latticed apophyses, either on each radial spine or only on a part of the twenty spines.

The genus Lithoptera, founded by Johannes Müller in 1858 for the first observed Mediterranean species, Lithoptera fenestrata, differs from all other Quadrilonchida in the fenestrated form of the apophyses, which he compared to the sails of a windmill. This peculiar fenestration is effected by two to four parallel pairs of opposite apophyses, which are crossed by perpendicular branches, parallel to the spine itself. Therefore the wings or lattice-plates have quadrangular meshes and lie in one meridian plane of the spine, not in a tangential plane (as in the Acanthophracta). Commonly the lateral ends of the four broad equatorial wings are so crossed that one lateral corner of each wing lies on the upper, the other corner on the under side of both its neighbours; but sometimes the meeting corners have grown together.

Subgenus 1. Lithopteranna, Haeckel.

Definition.—Four equatorial spines with transverse apophyses; sixteen others (eight tropical and eight polar spines) simple, without apophyses.

1. Lithoptera tetraptera, n. sp. (Pl. 131, fig. 9).

Four equatorial spines spindle-shaped, with latticed apophyses, each crossed by two transverse beams which are connected at equal distances by four rods parallel to the spine (therefore each wing with four square meshes in a single row). Lateral corners of the neighbouring wings not meeting. Sixteen smaller spines (eight tropical and eight polar) simple, conical, without apophyses.

Dimensions.—Diagonal of the square body 0.24; length of the inner square 0.16.

Habitat.—Tropical Atlantic, Station 348, surface.

2. Lithoptera mülleri, Haeckel.

Lithoptera mülleri, Haeckel, 1862, Monogr. d. Radiol., p. 398, Taf. xx. figs. 1, 2.

Four equatorial spines four-edged, with large latticed apophyses, each crossed by three transverse beams, which are connected at irregular distances by eight to twelve rods parallel to the spine (therefore each wing with two rows of rectangular meshes). The wings are placed not perfectly in the equatorial plane, but a little obliquely, so that each wing lies with one lateral corner on the upper, with the other corner on the under side of its neighbours. Sixteen smaller spines simple, thin, cylindrical, without apophyses.

Dimensions.—Diagonal of the square body 0.3; length of the inner square 0.17.

Habitat.—Mediterranean (Messina), surface.

3. Lithoptera lamarckii, n. sp.

Four equatorial spines four-edged, with large latticed apophyses; each crossed by three transverse beams, which are connected at short distances by twelve to sixteen rods parallel to the spine (therefore each wing with two rows of hexagonal or nearly elliptical meshes). Wings placed as in Lithoptera mülleri. Sixteen smaller spines simple, thin, prismatic, without apophyses.

Dimensions.—Diagonal of the square body 0.35; length of the inner square 0.2.

Habitat.—Central Pacific, Station 271, surface.

4. Lithoptera tetragona, n. sp.

Four equatorial spines compressed, four-edged, with large latticed apophyses, each crossed by four transverse beams, which are connected at regular distances by eight to twelve rods parallel to the spine. (Therefore each wing with three rows of square meshes.) Wings placed in the equatorial plane and grown together by their meeting lateral ends, forming a square equatorial girdle of lattice-work. Sixteen smaller spines simple, thin, prismatic, without apophyses.

Dimensions.—Diameter of the square body 0.4; length of the inner square 0.22.

Habitat.—North Pacific, Station 244, surface.

Subgenus 2. Lithopterella, Haeckel.

Definition.—Twelve spines (four equatorial and eight tropical) with transverse apophyses; the eight polar spines simple, without apophyses.

5. Lithoptera quadrata, n. sp. (Pl. 131, fig. 10).

Twelve spines with transverse apophyses; eight (polar) spines simple, small, without apophyses. Four equatorial spines very large and stout, compressed, each crossed by four transverse beams, which are connected by eight to ten rods parallel to the spine (therefore each wing with three rows of irregular rectangular meshes). Wings placed in the equatorial plane and grown together by their meeting lateral ends, forming a square equatorial girdle of lattice-work. Eight tropical spines thin, crossed by a long and thin transverse beam, which bears on its distal side eight to ten rods parallel to the spine.

Dimensions.—Diagonal of the square body 0.35; length of the inner square 0.18.

Habitat.—South Atlantic, Station 326, surface.

6. Lithoptera dodecaptera, n. sp.

Twelve spines with transverse apophyses; eight (polar) spines simple, small, without apophyses. Four equatorial spines very large, quadrangular; each crossed by three transverse beams, which are connected by ten to twelve rods parallel to the spine (therefore each wing with two rows of square meshes). Wings placed as in Lithoptera mülleri. Eight tropical spines much thinner, crossed each by two transverse beams, which are connected by six to eight rods parallel to the spine (therefore each wing with one row of rectangular meshes).

Dimensions.—Diagonal of the square body 0.4; length of the inner square 0.25.

Habitat.—Central Pacific, Station 271, surface.

Subgenus 3. Lithopteromma, Haeckel.

Definition.—All twenty spines with transverse apophyses.

7. Lithoptera darwinii, Haeckel.

Lithoptera darwinii, Haeckel, 1879, Natürl. Schöpfungsgesch., Aufl. vii. p. 706, Taf. xvi. fig. 12.

All twenty spines with transverse apophyses; these are quite simple in the eight small cross-shaped polar spines; also simple, but bearing some perpendicular rods, in the eight thin tropical spines. Four equatorial spines very large and stout, each crossed by four transverse beams, which are connected by eight to ten rods parallel to the spine (therefore each wing with three rows of irregular rectangular meshes). Wings placed in the equatorial plane and grown partly together by their meeting lateral ends.

Dimensions.—Diagonal of the square body 0.4; length of the inner square 0.2.

Habitat.—South-east Pacific, west coast of Patagonia, Station 302, surface.

8. Lithoptera icosaptera, n. sp.

All twenty spines with transverse apophyses, bearing one to three rows of rectangular meshes; eight polar spines small, each with a single row; eight tropical spines long and thin, each with two parallel rows. Four equatorial spines much larger and thicker, each with three parallel transverse rows of meshes. All twenty wings free, not grown together by their lateral ends.

Dimensions.—Diagonal of the square body 0.48; length of the inner square 0.24.

Habitat.—Indian Ocean, Belligemma, Ceylon (Haeckel), surface.

9. Lithoptera fenestrata, J. Müller.

Lithoptera fenestrata, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 154, Taf. xi. fig. 13.

All twenty spines with transverse apophyses, bearing one to three rows of irregular, rectangular meshes; eight polar and eight tropical spines small, each with a single row of meshes (between two parallel transverse beams). Four equatorial spines little larger, each with two rows (between three parallel transverse beams). Central capsule filled up with green pigment.

Dimensions.—Diagonal of the square body 0.3; length of the inner square 0.2.

Habitat.—Mediterranean (Saint Tropez, Nice).

Family XXXVIII. Amphilonchida, Haeckel (Pl. 132).

Acantholonchida (Amphilonchida et Amphilithida), Haeckel, 1881, Prodromus, p. 466.

Definition.—Acantharia with twenty radial spines of very unequal size, disposed according to the law of the Icosacantha; two opposite equatorial spines (in the longitudinal axis) much larger than the eighteen others. No lattice-shell.

The family Amphilonchida is distinguished from all other Acanthometra by the excessive development of two opposite equatorial spines, which are much larger than the eighteen other spines. In my Monograph (1862, p. 389) I had united all these Acanthonida in a single genus Amphilonche (with ten species). Some species of it are very common and widely distributed; but in general the number of different forms in this family is much smaller than in the two foregoing families.

The two principal spines, which in all Amphilonchida are much larger than the eighteen other spines, characterise the "hydrotomical axis" or the larger equatorial axis. The two other equatorial spines or the "geotomical spines" are much smaller, and commonly of the same size as the eight tropical and the eight polar spines. In the genera Amphilonche and Amphibelone these eighteen smaller spines are rather equally developed; sometimes they are very small or quite rudimentary, so that the skeleton seems to be represented only by the two very long principal spines (Pl. 132, fig. 4). The genus Acantholonche is distinguished by the unequal size of the eight tropical and the eight polar spines, the latter being more or less rudimentary. However, the central bases of all twenty spines, by which they are united in the centre, are constantly present. The genus Amphibelone is distinguished by the unequal size and form of the two principal spines, one of them the "caudal spine," being larger (and often of another form) than the opposite "frontal spine."

The form of the radial spines is in the Amphilonchida far less varied and complicated than in the other Acanthonida (the Astrolonchida and Quadrilonchida). Apophyses or lateral transverse processes are never developed. The three main forms of spines are the same as in the other Acanthonida; they are (1) either cylindrical or conical (like Acanthometron), or (2) compressed or two-edged (like Zygacantha), or (3) quadrangular or four-edged (like Acanthonia). Often the spines are angular in the inner or proximal, roundish in the outer or distal part. The distal apex is commonly simple, conical or pyramidal. The central base is commonly also pyramidal, as in the majority of the Acanthonida; and the triangular faces of the neighbouring bases are simply propped one upon another. More rarely a basal leaf-cross is developed above the basal pyramid. Very rarely the central bases of the united spines grow together in the centre, so that the whole skeleton forms a single piece of acanthin.

The Central Capsule is rarely spherical, commonly prolonged in the direction of the hydrotomical axis; ellipsoidal or cylindrical, sometimes also four-sided prismatic; it commonly envelops the greater part of the two principal spines; its structure and contents are the same as in the other Acanthonida.

Synopsis of the Genera of Amphilonchida.

Eighteen smaller spines of nearly equal size and similar form. Two opposite large principal spines (frontal and caudal) equal, 341. Amphilonche.

Caudal spine larger than the frontal spine, 342. Amphibelone.

Eight tropical and eight polar spines of different sizes (the latter often rudimentary), 343. Acantholonche.

Eighteen smaller spines of nearly equal size and similar form.

Two opposite large principal spines (frontal and caudal) equal,

341. Amphilonche.

Caudal spine larger than the frontal spine,

342. Amphibelone.

Eight tropical and eight polar spines of different sizes (the latter often rudimentary),

343. Acantholonche.

Genus 341. Amphilonche,^[381] Haeckel, 1862, Monogr. d. Radiol., p. 389.

Definition.—Amphilonchida with two equal principal spines (frontal and caudal spines not different); the eighteen smaller spines nearly equal.

The genus Amphilonche represents the original and at the same time the most common form of Amphilonchida; the two opposite principal spines are of equal size and form, much larger (and often also of another form) than the eighteen smaller spines; these latter exhibit no marked differences in size and form.

Subgenus 1. Amphiloncharium, Haeckel.

Definition.—Spines in the centre united by triangular faces of their pyramidal bases, propped one upon another. No basal leaf-cross.

1. Amphilonche belonoides, Haeckel.

Amphilonche belonoides, Haeckel, 1862, Monogr. d. Radiol., p. 392, Taf. xvi. fig. 6, Taf. xviii. fig. 21.

Acanthometra belonoides, Haeckel, 1860, Monatsber. d. k. Akad. d. Wiss. Berlin, p. 808.

Two principal spines cylindrical, of equal breadth throughout their whole length, with simple conical apex; base a small pyramid, without leaf-cross. Eighteen smaller spines conical, much shorter, with simple bristle-shaped apex. Central capsule spindle-shaped or cylindrical, yellow.

Dimensions.—Length of the two major spines 0.4 to 0.8, of the eighteen minor 0.05 to 0.2.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific, surface.

2. Amphilonche lanceolata, n. sp. (Pl. 132, fig. 1).

Two principal spines compressed, lanceolate, two-edged, gradually tapering from the broader middle towards the two ends; apex simple; base a large pyramid, with broad leaf-cross. Eighteen smaller spines about half as long, pyramidal, with simple conical or bristle-shaped apex. Central capsule lentelliptical, pink, opaque.

Dimensions.—Length of the two major spines 0.2, of the eighteen minor 0.1.

Habitat.—Tropical Atlantic, Station 343, surface.

3. Amphilonche diodon, n. sp. (Pl. 132, fig. 3).

Two principal spines compressed, lanceolate, two-edged, tapering from the broader middle towards the two ends; apex simple; base a small pyramid, without leaf-cross. Eighteen smaller spines sword-shaped, only two-thirds or one-half as long, and one-third or one-fourth as broad, each with two opposite teeth in the distal part. Central capsule ellipsoidal.

Dimensions.—Length of the two major spines 0.13, breadth 0.02; length of the eighteen minor spines 0.1.

Habitat.—North Atlantic, Station 352, surface.

4. Amphilonche tenuis, Haeckel.

Amphilonche tenuis, Haeckel, 1862, Monogr. d. Radiol., p. 389, Taf. xvi. fig. 1, Taf. xviii. fig. 16.

Acanthometra tenuis, Haeckel, 1860, Monatsber. d. k. Akad. d. Wiss. Berlin, p. 807.

Two principal spines quadrangular prismatic, with smooth edges, slightly or not at all prominent, of equal breadth throughout their whole length; apex simple or bifid; base a small pyramid, without leaf-cross. Eighteen smaller spines of the same form, but only one-fourth or one-third as long. Central capsule spherical or ellipsoidal, colourless.

Dimensions.—Length of the two major spines 0.2 to 0.3, of the eighteen minor spines 0.05 to 0.1.

Habitat.—Mediterranean (Messina); Atlantic, Station 354, Canary Islands, surface.

5. Amphilonche denticulata, Haeckel.

Amphilonche denticulata, Haeckel, 1862, Monogr. d. Radiol., p. 390, Taf. xvi. fig. 2, Taf. xviii. fig. 17.

Two principal spines quadrangular prismatic, with prominent, elegantly denticulated edges, of equal breadth throughout their whole length; apex simple or truncated; base a small pyramid, without leaf-cross. Eighteen smaller spines of the same form, but only one-fourth or one-third as long. Central capsule ellipsoidal, opaque, yellowish-brown.

Dimensions.—Length of the two major spines 0.3 to 0.4, of the eighteen minor 0.1; breadth of the former 0.009, of the latter 0.006.

Habitat.—Mediterranean (Messina), Haeckel, surface.

6. Amphilonche heteracantha, Haeckel.

Amphilonche heteracantha, Haeckel, 1862, Monogr. d. Radiol., p. 293, Taf. xvi. fig. 7.

Acanthometra heteracantha, Haeckel, 1860, Monatsber. d. k. Akad. d. Wiss. Berlin, p. 808.

Two principal spines quadrangular prismatic, very large, with four broad, prominent, lamellar edges, of equal breadth throughout their whole length. Apex as well as the base a four-sided pyramid. Eighteen smaller spines very thin, conical, with bristle-shaped apex; base a small pyramid, without leaf-cross. Central capsule cylindrical or violin-shaped, opaque yellow.

Dimensions.—Length of the two major spines 0.2 to 0.3, breadth 0.015 to 0.02; length of the eighteen minor spines 0.1 to 0.15, basal breadth 0.004 to 0.008.

Habitat.—Mediterranean (Messina); Central Pacific, Station 271, surface.

7. Amphilonche elongata, Haeckel.

Amphilonche elongata, Haeckel, 1862, Monogr. d. Radiol., p. 392, Taf. xviii. figs. 22a, 22b.

Acanthometra elongata, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 48, Taf. vii. fig. 13.

Two principal spines quadrangular prismatic in the proximal half, cylindrical or spindle-shaped in the distal half, with simple apex; base a small pyramid, without leaf-cross. Eighteen smaller spines very thin, bristle-shaped, conical on the base, with small pyramid. Central capsule spindle-shaped, transparent, yellow.

Dimensions.—Length of the two major spines 0.3 to 0.5, breadth 0.01 to 0.03; length of the eighteen smaller spines 0.05 to 0.3.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, surface.

Subgenus 2. Amphilonchidium, Haeckel.

Definition.—Spines at the central base with a broad leaf-cross, composed of four prominent triangular lamellæ; between the meeting edges of the latter twenty-two pyramidal compartments or basal funnels.

8. Amphilonche ovata, Haeckel.

Amphilonche ovata, Haeckel, 1862, Monogr. d. Radiol., p. 390.

Acanthometra ovata, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 47, Taf. vii. fig. 10, Taf. ix. fig. 4.

Two principal spines cylindrical, of equal breadth throughout their whole length, with simple conical or bifid apex; base with a large leaf-cross of double the breadth. Eighteen smaller spines of the same form, but thinner and only half as long. Central capsule ellipsoidal, brown, opaque.

Dimensions.—Length of the two major spines 0.3 to 0.4, breadth 0.008 to 0.012; length of the eighteen minor spines 0.1 to 0.2.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific, surface.

9. Amphilonche conica, n. sp. (Pl. 132, fig. 6).

Two principal spines conical, elongate, with simple apex; base thickened, with large leaf-cross. Eighteen smaller spines also conical, of about the same basal breadth, but only one-fourth to one-half as long. Central capsule ellipsoidal, pellucid.

Dimensions.—Length of the two major spines 0.15 to 0.2, basal breadth 0.03 to 0.04; length of the eighteen minor spines 0.05 to 0.1.

Habitat.—Central Pacific, Stations 265 to 274, surface.

10. Amphilonche lancetta, n. sp.

Two principal spines compressed, lanceolate, two edged, gradually tapering from the broader middle towards the two ends; apex simple; base of double the breadth, with a large leaf-cross. Eighteen smaller spines of the same form, but shorter and only half as broad. Central capsule lentelliptical, pellucid.

Dimensions.—Length of the two major spines 0.2 to 0.3, breadth in the middle part 0.02 to 0.03; length of the eighteen smaller spines 0.1 to 0.2.

Habitat.—South Pacific, Station 288, surface.

11. Amphilonche complanata, Haeckel.

Amphilonche complanata, Haeckel, 1862, Monogr. d. Radiol., p. 390, Taf. xvi. fig. 3, Taf. xviii. fig. 18, a, b.

Acanthometra complanata, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 808.

Two principal spines compressed, two-edged, linear, of equal breadth throughout their whole length; apex emarginate or bifid; base with a large leaf-cross of double the breadth. Eighteen smaller spines of the same form, but only one-fourth to one-half as large. Central capsule ellipsoidal, yellow, pellucid.

Dimensions.—Length of the two major spines 0.15 to 0.25, breadth 0.004 to 0.006; length of the eighteen minor spines 0.05 to 0.1.

Habitat.—Mediterranean (Messina), surface.

12. Amphilonche messanensis, Haeckel.

Amphilonche messanensis, Haeckel, 1862, Monogr. d. Radiol., p. 391, Taf. xvi. fig. 4, Taf. xviii. fig. 19.

Acanthometra messanensis, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 808.

Two principal spines quadrangular prismatic, often a little compressed from two sides, of nearly equal breadth throughout their whole length; apex either truncate or emarginate, with two opposite teeth; base with a large leaf-cross of double the breadth. Eighteen smaller spines of similar form or more compressed, much shorter. Central capsule spherical or ellipsoidal, yellow, transparent.

Dimensions.—Length of the two major spines 0.12 to 0.18, breadth 0.016; length of the minor spines 0.05 to 0.09.

Habitat.—Mediterranean (Messina, Corfu), Haeckel, surface.

13. Amphilonche hydrotomica, n. sp. (Pl. 132, fig. 2).

Two principal spines quadrangular prismatic, with four broad prominent lamellar edges or wings, of equal breadth throughout their whole length; apex pyramidal; base with a large leaf-cross. Eighteen smaller spines cylindrical or bristle-shaped, only half as long and very thin. Central capsule cylindrical or spindle-shaped, very long, opaque.

Dimensions.—Length of the two major spines 0.1 to 0.2, breadth 0.02 to 0.03; length of the eighteen minor spines 0.05 to 0.1.

Habitat.—Central Pacific, Stations 270 to 274, surface.

14. Amphilonche violina, n. sp. (Pl. 132, fig. 5).

Two principal spines quadrangular prismatic, nearly violin-shaped, with four very broad, prominent, lamellar wings, which are constricted in the middle part, and broadened towards the two ends; apex truncate pyramidal; base with a large leaf-cross. Eighteen smaller spines much shorter, of equal breadth at the base, assuming the form of a quadrangular pyramid, thin prismatic in the distal half. Central capsule spindle-shaped, opaque.

Dimensions.—Length of the two major spines 0.15 to 0.18, breadth 0.02 to 0.025; length of the eighteen minor spines 0.04 to 0.08.

Habitat.—Central Pacific, Station 271, surface.

15. Amphilonche tetraptera, Haeckel.

Amphilonche tetraptera, Haeckel, 1862, Monogr. d. Radiol., p. 391, Taf. xvi. fig. 5, Taf. xviii. fig. 20.

Acanthometra tetraptera, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 808.

Two principal spines four-sided pyramidal, with four broad lamellar prominent edges; apex simple or bifid; base with a large leaf-cross. Eighteen smaller spines of similar form, but only half as large. Central capsule spherical, opaque.

Dimensions.—Length of the two major spines 0.2, breadth on the base 0.025; length of the eighteen minor spines 0.1.

Habitat.—Mediterranean (Messina); North Atlantic, Canary Islands, Stations 352 to 354, surface.

Subgenus 3. Amphilithium, Haeckel, 1881, Prodromus, p. 466.

Definition.—Spines in the basal part grown together, so that the whole skeleton represents a single piece of acanthin; a star with two larger and eighteen smaller rays.

16. Amphilonche concreta, n. sp. (Pl. 132, figs. 4, 4a).

Two principal spines cylindrical, very long, of equal breadth throughout their whole length, with simple conical apex. Eighteen smaller spines short, conical or bristle-shaped, scarcely one-fourth or one-tenth as long, often quite rudimentary. All twenty spines perfectly grown together in the centre, forming a single piece of acanthin (derived from Amphilonche belonoides by central concrescence; often the sutures of the concreted bases are visible, fig. 4a).

Dimensions.—Length of the two major spines 0.1 to 0.4, breadth 0.005 to 0.015; length of the eighteen minor spines 0.005 to 0.15.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific, surface.

17. Amphilonche acufera, n. sp.

Two principal spines thick, four-sided prismatic in the basal half, cylindrical or spindle-shaped in the distal half, with simple conical apex. Eighteen smaller spines shorter, thin, bristle-shaped or conical on the base. All twenty spines in the centre perfectly grown together, forming a single piece of acanthin. (Derived from Amphilonche elongata by central concrescence.)

Dimensions.—Length of the two major spines 0.3 to 0.5, breadth 0.01 to 0.03; length of the eighteen minor spines 0.08 to 0.2.

Habitat.—Central Pacific, Stations 266 to 274, surface.

Genus 342. Amphibelone,^[382] Haeckel, 1862, Monogr. d. Radiol., p. 392.

Definition.—Amphilonchida with two unequal principal spines (the frontal spine very different from the caudal spine); the eighteen smaller spines nearly equal.

The genus Amphibelone exhibits among the Amphilonchida the same remarkable differentiation of the two principal or longitudinal spines, as Zygostaurus among the Quadrilonchida; the frontal spine differs commonly from the caudal spine not only in its size, but also in its peculiar form; commonly one pole of the longitudinal axis is much more strongly developed than the other. The eighteen smaller spines are nearly equal.

Subgenus 1. Amphibelonium, Haeckel.

Definition.—All twenty spines separate, but in contact in the centre and resting one against another by the triangular sides of their pyramidal bases, without a prominent basal leaf-cross.

1. Amphibelone aciculata, n. sp.

Two principal spines thick, without edges and wings, the frontal spine short, spindle-shaped, the caudal three to six times as long, cylindrical, both of equal breadth, with simple conical apex and simple pyramidal base, without leaf-cross. Eighteen smaller spines very thin, bristle-shaped, of the same length as the frontal spine. Central capsule cylindrical or spindle-shaped, enveloping the two principal spines nearly throughout their whole length.

Dimensions.—Length of the frontal spine 0.2 to 0.4, of the caudal spine 1.0 to 2.0; breadth of both 0.01; length of the eighteen smaller spines 0.1 to 0.3.

Habitat.—South Atlantic, Station 325, surface.

2. Amphibelone cultellata, n. sp. (Pl. 132, fig. 10).

Two principal spines broad, two-edged, knife-shaped; two opposite in the equatorial plane, thin and broad wings or lamellæ are developed, and these enclose the proximal part of both spines, whilst their distal part is free, cylindrical, with conical apex: the two wings of the longer caudal spine are lanceolate, twice to four times as broad as the two wings of the shorter frontal spine; their base is a simple pyramid without leaf-cross. Eighteen smaller spines conical, with bristle-shaped prolongation, one-fourth to one-half as long as the frontal spine. Central capsule green, semitransparent.

Dimensions.—Length of the frontal spine 0.1 to 0.2, breadth 0.02 to 0.03; length of the caudal spine 0.2 to 0.4, breadth 0.04 to 0.08; length of the eighteen smaller spines 0.05 to 0.15.

Habitat.—Indian Ocean, Maldive Islands (Haeckel), surface.

3. Amphibelone pyramidata, n. sp. (Pl. 132, fig. 9).

Two principal spines four-winged, with four crossed, very thin and broad wings, which are somewhat broader in the convex middle part than at either end; both ends of each spine four-sided pyramidal, with four concave edges and a very small terminal pyramid; base without leaf-cross. The longer caudal spine is twice as broad at the distal end as at its proximal end, and three times as broad as the distal end of the shorter frontal spine. Eighteen smaller spines bristle-shaped, with four-sided pyramidal bases. Central capsule pyramidal, enveloping the two principal spines throughout their whole length; the base of the slender quadrangular pyramid is on the caudal, the apex on the frontal pole of the longitudinal axis.

Dimensions.—Length of the frontal spine 0.2 to 0.25, distal breadth 0.01; length of the caudal spine 0.3 to 0.4, distal breadth 0.03; length of the eighteen smaller spines 0.04 to 0.08.

Habitat.—Cape of Good Hope, Station 143, depth 1900 fathoms.

4. Amphibelone anomala, Haeckel.

Amphilonche anomala, Haeckel, 1862, Monogr. d. Radiol., p. 394, Taf. xvi. fig. 8, Taf. xviii. figs. 23a, 23b.

Acanthometra anomala, Haeckel, 1860, Monatsber. d. k. Akad. d. Wiss. Berlin, p. 808.

Two principal spines four-winged, nearly prismatic, with four crossed, very broad and thick wings; both ends of each spine four-sided pyramidal, with four concave edges and a very small terminal pyramid; base without leaf-cross. The edges of the four wings are concave on the shorter frontal, convex on the longer caudal spine. Eighteen smaller spines only one-fourth to one-half as long, linear, two-edged, with two parallel teeth on the distal end. Central capsule four-sided prismatic, olive-green, enveloping almost completely the two principal spines.

Dimensions.—Length of the frontal spine 0.12, middle breadth 0.016; length of the caudal spine 0.14, middle breadth 0.024; length of the eighteen smaller spines 0.04 to 0.06.

Habitat.—Mediterranean (Messina), surface.

Subgenus 2. Amphibelithium, Haeckel.

Definition.—All twenty spines grown together in the centre, forming a single star-shaped piece of acanthin.

5. Amphibelone clavaria, n. sp.

Two principal spines roundish, without edges and wings; the smaller frontal spine elongate conical, the larger caudal spine two to four times as long, cylindrical, in the distal part spindle-shaped or club-shaped, with conical apex. Central base simple pyramidal, without leaf-cross. Eighteen smaller spines much shorter, bristle-shaped. Central capsule very long, club-shaped. All twenty spines perfectly grown together in the centre.

Dimensions.—Length of the frontal spine 0.12, of the caudal spine 0.4 to 0.8; frontal breadth 0.01, caudal breadth 0.03; length of the eighteen smaller spines 0.05.

Habitat.—Central Pacific, Station 272, surface.

Genus 343. Acantholonche,^[383] Haeckel, 1881, Prodromus, p. 466.

Definition.—Amphilonchida with two equal principal spines (frontal and caudal spines not different). The eighteen smaller spines are very unequal, ten of them (eight tropical and two transverse equatorial spines) much larger than the rudimentary eight polar spines.

The genus Acantholonche differs from its ancestral genus Amphilonche in the different shape of the eight tropical and the eight polar spines; these latter are much smaller than the former, which are almost equal to the two transverse equatorial spines. The two principal spines are equal, but in size and shape very different from the others.

1. Acantholonche amphipolaris, n. sp. (Pl. 132, fig. 7).

Two principal spines stout, quadrangular prismatic in the basal half, cylindrical or spindle-shaped in the distal half, with simple conical apex; base a small pyramid without leaf-cross. Two transverse and eight tropical spines, about half as long as the former, very thin, bristle-shaped, conical at the basal part. Eight polar spines very small, scarcely one-eighth or one-fourth as long as the latter, short pyramidal or conical, often quite rudimentary. Central capsule cylindrical, enveloping the basal half of the two principal spines.

Dimensions.—Length of the two principal spines 0.4 to 0.5, of the ten smaller spines 0.2 to 0.3, of the eight rudimentary polar spines 0.01 to 0.06; breadth of the two large spines 0.02 to 0.03.

Habitat.—Central Pacific, Stations 266 to 274, surface.

2. Acantholonche peripolaris, n. sp. (Pl. 132, fig. 8).

Two principal spines quadrangular prismatic, with four broad prominent lamellar wings, of increasing breadth towards the pyramidal distal apex. Both ends of each spine four-sided pyramidal, base without leaf-cross. Two transverse and eight tropical spines about two-thirds as long as the former, four-sided pyramidal in the basal half, conical in the distal half, often curved. Eight polar spines very small, about one-fourth as long as the latter, short conical or pyramidal. Central capsule four-sided prismatic, enveloping both principal spines.

Dimensions.—Length of the two principal spines 0.2, of the ten smaller spines 0.12, of the eight rudimentary polar spines 0.04.

Habitat.—Central Pacific, Station 274, surface.

Order IV. ACANTHOPHRACTA, Richard Hertwig, 1879.

Definition.—Acantharia with complete latticed shell.

The order Acanthophracta, the fourth order of Radiolaria, comprises all those Acantharia in which the acanthinic skeleton is a complete latticed or fenestrated shell, supported by radial spines arising from one common central point. By the possession of such a complete shell the Acanthophracta differ from their ancestral group, the nearly allied Acanthometra, which represent the older and simpler, first order of Acantharia. All Acanthophracta are Icosacantha (like the Acanthonida, their ancestral group), and possess twenty radial spines disposed according to the Müllerian law (compare above, p. 717).

Johannes Müller, who first observed five representatives of this order, called a part of them "Acanthometræ cataphractæ," and united these with the true Acanthometra (Acanthometra costata and Acanthometra cataphracta; Abhandl. d. k. Akad. d. Wiss. Berlin, 1858, pp. 12, 49). Another part was united by him with the true Haliomma (Haliomma echinoides, Haliomma hystrix, Haliomma tabulatum; Abhandl. d. k. Akad. d. Wiss. Berlin, 1858, pp. 36, 37). He supposed that these latter formed the immediate transition from the true Acanthometra to the true Haliomma, and that their skeleton was siliceous.

In my Monograph (1862, p. 412) I founded a separate subfamily, Dorataspida, for the "Acanthometræ cataphractæ," which I considered as the first subfamily of the "Ommatida." That subfamily contained at that time only two genera, Dorataspis (with seven species) and Haliommatidium (with five species). A third genus, Aspidomma (with two species), was united by me with the Haliommatida (because of its double shell). For a fourth genus (Diploconus) with a single species I founded the peculiar family of Diploconida. Therefore the whole number of Acanthophracta described in my Monograph amounted only to four genera and fifteen species. Now the rich collections of the Challenger have added such a great number of new forms, that we may distinguish here thirty-eight genera and two hundred and twelve species.

Richard Hertwig in his excellent work (Der Organismus der Radiolarien, 1879, p. 25) separated his "Acanthophractida" perfectly from the "Ommatida" (or the siliceous Sphæroidea), and united them with the "Acanthometrida" in his order "Acanthometrea." But he separated them also from the nearly allied Diploconida, following my former arrangement. He distinctly noted that the skeleton in all these Acanthophractida (as well as in the Acanthometrida) consists not of silex but of the organic substance "acanthin."

The astonishing number of new and interesting forms of Acanthophracta which I have found in the rich collection of the Challenger enables me to distinguish now in this suborder six different families, two of which are perfectly new (the Sphærocapsida and the Hexalaspida). But the four other families also are so much enlarged that their interesting morphology appears in quite a new and clear light. Far the largest and most important of these six families is that of the true Dorataspida, which embraces seventeen genera and one hundred and eight species (more than the other five families together). From this largest and oldest ancestral family four other families have afterwards arisen, whilst a single family, the Sphærocapsida, seems to possess no direct phylogenetic connection with the five other families.

The peculiar and quite new family of Sphærocapsida (Pl. 133, figs. 7-11; Pl. 135, figs. 6-10) differs from all other Acanthophracta in the singular structure of the spherical acanthinic shell, composed of innumerable small plates or aglets, each of which is pierced by a very small porule. This peculiar pavemented shell (enclosing the central capsule and separated from it by the jelly-like calymma) seems to be produced on the surface of the spherical calymma, immediately by secretion of the pseudopodia, and independently from the twenty radial spines, united in the centre of the sphere. On the twenty points, where the spines perforate the shell, there are originally eighty larger pores (four around each piercing spine); but there is no certain indication that the shell is produced by the meeting apophyses of the twenty spines, as is the case in the five other families of Acanthophracta. Therefore perhaps it is more natural to unite these latter into another suborder as Cladophracta, and to separate them from the Sphærocapsida, which may be called Capsophractæ.

The Dorataspida (Pls. 134-138), the common ancestral stock of the Cladophracta, in the definition here restricted embraces all those Acanthophracta in which the spherical lattice-shell is simple and composed of the meeting branches of twenty radial spines united in its centre. As already pointed out above, this family is probably diphyletic, and embraces two subfamilies which have been derived originally from two different forms of Acanthonida—the Diporaspida (with two opposite apophyses on each spine) derived from the Phractacanthida, and the Tessaraspida (with four crossed apophyses on each spine) derived from the Stauracanthida; in the former we find originally forty apophyses, in the latter eighty apophyses, by the meeting branches of which the spherical lattice-shell originates. The four following families of Acanthophracta have probably been derived from the Diporaspida.

The Phractopeltida (Pl. 133, figs. 1-6) differ from all other Acanthophracta in the possession of a double lattice-shell, composed of two concentric spheres which are united by the twenty radial spines meeting in the centre. As all Phractopeltida possess originally only two apophyses on each radial spine, they must be derived from the Diporaspida (Orophaspis), and bear to them the same relation as the Dyosphærida do to the Monosphærida. As the spherical central capsule of the Phractopeltida is enclosed between both shells, smaller than the outer, larger than the inner shell, the latter may be called "medullary shell," the former "cortical shell." This family represents among the Acanthophracta only the "Diplophracta," whilst all others are "Haplophracta."

The three families here characterised may be called together "Sphærophracta," as their central capsule and the enveloping shell are constantly spherical (or the shell sometimes an "endospherical polyhedron"). On the contrary the following three families of Acanthophracta may be united as "Prunophracta," as their central capsule and shell are never spherical, but either ellipsoidal or lenticular or of another form. The common ancestral stock of this suborder are the Belonaspida, in which the form of the central capsule and the enclosing lattice-shell is ellipsoidal; they are derived from the Dorataspida (and probably all from the subfamily Diporaspida) by the prolongation of two opposite radial spines which are larger than the eighteen others; they are the two equatorial spines of the "hydrotomical axis" (compare above, p. 719, and Pl. 136, figs. 6-9).

The Hexalaspida (Pl. 139) represent a new and very remarkable family, distinguished from all other Acanthophracta by the preponderating development of six stout radial spines, which are much larger than the fourteen others. These six principal spines lie in one meridian plane of the shell (in the "hydrotomical plane," p. 720), and are the two opposite equatorial spines and the four appertaining polar spines of the same plane. As the fourteen smaller spines develop their apophyses at smaller distances from the centre, the shell assumes a peculiar lenticular or discoidal form, and the margin of this disk bears the six larger spines. Moreover the enclosed small central capsule is lenticular. The Hexalaspida may be derived immediately from the Belonaspida.

The Diploconida (Pl. 140) form the last and the most modified family of all Acanthophracta. The remarkable shell exhibits the strange form of a double cone, bearing in its axis two very large opposite spines; these are the two equatorial spines of the "hydrotomical axis" (p. 719). The double-conical or nearly cylindrical shell is composed of three different parts or segments; the small middle part is the true lattice-shell of the Hexalaspida and Belonaspida, and bears the eighteen smaller (often quite rudimentary) radial spines. The two other parts (opposite on both poles of its hydrotomical axis) are the conical or cylindrical, solid, basal sheaths of the two large equatorial spines, enveloping their major part. In consequence of this peculiar metamorphosis of the shell the Diploconida represent the last and the most aberrant group of all Acantharia.

Synopsis of the Suborders and Families of Acanthophracta.

Suborder I. SPHÆROPHRACTA. Twenty radial spines of equal size. Shell spherical (or an endospherical polyhedron). Shell spherical, simple, pierced by twenty or eighty aspinal pores and composed of a pavement of innumerable very small plates or aglets, each pierced by one porule, 1. Sphærocapsida.

Shell spherical, simple, composed of the meeting branches of two or four apophyses of the twenty radial spines, 2. Dorataspida.

Shell spherical, double, composed of two concentric lattice-spheres, which are connected by the twenty radial spines and composed of the meeting branches of their apophyses, 3. Phractopeltida.

Suborder II. PRUNOPHRACTA. Twenty radial spines of unequal size; two or six hydrotomical spines much larger than the eighteen or fourteen others. Shell not spherical. Shell ellipsoidal, with prolonged hydrotomical axis, the two spines of which are larger than the eighteen others, 4. Belonaspida.

Shell lenticular or discoidal, with six larger spines placed in the hydrotomical plane (fourteen other spines much smaller), 5. Hexalaspida.

Shell diploconical or nearly cylindrical, with two opposite large funnels, the sheaths of the enlarged two spines of the hydrotomical axis (eighteen other spines much smaller or rudimentary), 6. Diploconida.

Suborder I. SPHÆROPHRACTA. Twenty radial spines of equal size. Shell spherical (or an endospherical polyhedron).

Shell spherical, simple, pierced by twenty or eighty aspinal pores and composed of a pavement of innumerable very small plates or aglets, each pierced by one porule,

1. Sphærocapsida.

Shell spherical, simple, composed of the meeting branches of two or four apophyses of the twenty radial spines,

2. Dorataspida.

Shell spherical, double, composed of two concentric lattice-spheres, which are connected by the twenty radial spines and composed of the meeting branches of their apophyses,

3. Phractopeltida.

Suborder II. PRUNOPHRACTA. Twenty radial spines of unequal size; two or six hydrotomical spines much larger than the eighteen or fourteen others. Shell not spherical.

Shell ellipsoidal, with prolonged hydrotomical axis, the two spines of which are larger than the eighteen others,

4. Belonaspida.

Shell lenticular or discoidal, with six larger spines placed in the hydrotomical plane (fourteen other spines much smaller),

5. Hexalaspida.

Shell diploconical or nearly cylindrical, with two opposite large funnels, the sheaths of the enlarged two spines of the hydrotomical axis (eighteen other spines much smaller or rudimentary),

6. Diploconida.

Suborder I. SPHÆROPHRACTA, Haeckel.

Definition.—Shell spherical, with twenty radial beams of equal size.

Family XXXIX. Sphærocapsida, Haeckel (Pl. 133, figs. 7-11; Pl. 135, figs. 6-10).

Sphærocapsida, Haeckel, 1881, Prodromus, p. 469.

Definition.—Acantharia with simple spherical porous shell, composed of innumerable very small plates, each of which is pierced by one radial porule. Twenty radial spines of equal size meeting in the centre of the shell and disposed according to the Müllerian law of the Icosacantha, sometimes short and enclosed in the shell, at other times long and piercing it (rarely rudimentary or quite absent). Shell pierced therefore either by twenty larger perspinal pores or by eighty smaller aspinal pores. Central capsule spherical, enclosed in the porous shell.

The family Sphærocapsida, founded by me in 1881 for the single genus Sphærocapsa, represents a very peculiar and remarkable group of the Acanthophracta, very different from the five other families of this suborder, and probably derived, independently of them, directly from the Acanthonida. Whilst the lattice-shell of the five other families is composed of the meeting branches of lateral apophyses of the twenty spines, and its meshes are all or partly the intervals between these apophyses, in the Sphærocapsida the spherical shell has quite another structure, and is composed of innumerable small plates (each with one pore) which are secreted on the surface of the spherical calymma, independently of the twenty radial spines, which do not possess true apophyses.

In all Sphærocapsida the structure of the spherical shell is quite peculiar and different from that of all other Radiolaria. It is composed everywhere of innumerable very small plates or aglets, which are connected irregularly like paving-stones, and form a single continuous layer or pavement on the surface of the spherical calymma (Pl. 133, fig. 11, a; Pl. 135, figs. 8, 10). The small plates or paving-stones, which we will call "aglets," are connected at their meeting edges by a kind of cement, and form together with it a continuous thick capsule of acanthin. The form of the aglets is commonly more or less irregular, roundish or polygonal, sometimes longish (Pl. 133, fig. 11, a), more rarely it becomes rather regular, hexagonal, square, or roundish (Pl. 135, fig. 8). Usually all aglets of one and the same individual are of nearly equal size, between 0.01 and 0.02 in diameter, rarely less or more. The outer face of the aglets is more or less concave, so that the elevated meeting edges of the neighbouring aglets commonly form together a prominent network of crests (Pl. 135, figs. 8, 10); rarely the meeting edges partly cover one another like squamules (Pl. 133, fig. 11, a). Each small plate or aglet is pierced in its centre by a single radial canalicule or porule. The dimpled surface, so produced, resembles somewhat the dimpled plates of Ceriaspis, &c. Different from these innumerable very small dimples of the surface are the twenty larger "spinal dimples," or the concave larger plates, which are originally pierced by the twenty radial spines. Before we describe these, we must examine the spines themselves.

The twenty radial spines of all observed Sphærocapsida (sixteen species) agree perfectly with those of the genus Acanthonia (p. 749), and especially with Acanthonia tetracopa, Acanthonia denticulata, &c. All twenty spines, regularly disposed according to the Müllerian law of the Icosacantha, are of equal size, constantly four-edged prismatic, of equal breadth throughout their whole length. The prominent four edges are parallel, sometimes smooth, at other times elegantly denticulated. The central bases of the twenty spines are pyramidal, without leaf-cross, and propped one upon another with their triangular faces, as in the majority of the Acanthonida.

The relation of the twenty radial spines to the spherical shell exhibits in the five genera described very peculiar and important differences. In the first described genus, in Sphærocapsa, the spines are exactly as long as the shell-radius, and therefore are not prominent over the surface of the shell, with which they are firmly connected; the truncated distal end of the spine lies therefore here in the surface of the shell itself, and is connected with it by its four edges, between which four open aspinal pores remain, as in Tessaraspis, &c. (Pl. 135, figs. 6-10). In the next allied genus, Astrocapsa (Pl. 133, figs. 9, 10), the spines are longer than the shell-radius, and therefore more or less prominent over its surface; the piercing part of each spine is also surrounded by four aspinal pores. In the two following genera, Porocapsa and Cannocapsa (Pl. 133, figs. 7, 8), the radial spines are shorter than the shell-radius and therefore quite hidden and withdrawn inside the shell, which they do not reach. But in the ideal prolongation of each spine the shell is pierced by a single large opening, the "perspinal pore" or "perspinal hole," composed of the four united aspinal pores. Whilst in Porocapsa the perspinal pores are simple, they are prolonged in Cannocapsa into cylindrical tubes, open at both ends. The twenty perspinal holes of these Porocapsida are therefore derived by confluence of the eighty original aspinal pores of the Astrocapsida and preserve the same regular disposition, according to the Müllerian law of the Icosacantha. Finally, the same law as is valid also in the last genus is found in Cenocapsa; here the radial spines have completely disappeared, and the whole skeleton is a simple sphere, but of the same structure, and with the same twenty perspinal pores as in Porocapsa. It is very interesting that this spineless Cenocapsa among the Acantharia exhibits the same shell (a simple hollow sphere) as a last reduced form, which Cenosphæra among the Sphærellaria produces as a primitive ancestral form of numerous genera.

The Central Capsule of the Sphærocapsida is spherical, constantly smaller than the enclosing concentric shell, and separated from it by the calymma. Its structure seems to be the same as in the Acanthonida, and specially in the Astrolonchida. The pseudopodia (not yet observed) are probably protruded only through the twenty perspinal holes or the eighty aspinal pores.

Synopsis of the Genera of Sphærocapsida.

III. Subfamily Astrocapsida. Radial spines connected with the porous shell, as long or longer than its radius. Eighty aspinal pores. Spines as long as the radius, without external prolongation, 344. Sphærocapsa.

Spines longer than the radius, with external prolongation, 345. Astrocapsa.

III. Subfamily Porocapsida. Radial spines not connected with the porous shell, shorter than its radius. Twenty perspinal pores. Perspinal holes of the shell simple, without external prolongation, 346. Porocapsa.

Perspinal holes of the shell prolonged into radial centrifugal tubuli, 347. Cannocapsa.

III. Subfamily Cenocapsida. Radial spines disappeared. Twenty perspinal holes of the shell simple, without tubular prolongation, 348. Cenocapsa.

I. Subfamily Astrocapsida. Radial spines connected with the porous shell, as long or longer than its radius. Eighty aspinal pores.

Spines as long as the radius, without external prolongation,

344. Sphærocapsa.

Spines longer than the radius, with external prolongation,

345. Astrocapsa.

II. Subfamily Porocapsida. Radial spines not connected with the porous shell, shorter than its radius. Twenty perspinal pores.

Perspinal holes of the shell simple, without external prolongation,

346. Porocapsa.

Perspinal holes of the shell prolonged into radial centrifugal tubuli,

347. Cannocapsa.

III. Subfamily Cenocapsida. Radial spines disappeared.

Twenty perspinal holes of the shell simple, without tubular prolongation,

348. Cenocapsa.

Subfamily 1. Astrocapsida, Haeckel.

Definition.—Radial spines connected with the porous shell, as long as or longer than its radius. Therefore the shell pierced by eighty aspinal pores (four around each spine).

Genus 344. Sphærocapsa,^[384] Haeckel, 1881, Prodromus, p. 469.

Definition.—Sphærocapsida with twenty radial spines as long as the radius of the shell, without external prolongation; therefore their distal ends inserted in the perspinal holes, each of which is composed of four aspinal pores.

The genus Sphærocapsa is the most common form of the Sphærocapsida, and comprises those species in which the radial spines are as long as the radius of the shell, and therefore are connected with the margin of its aspinal holes, but not prolonged beyond its surface.

1. Sphærocapsa cruciata, n. sp. (Pl. 135, figs. 6, 7).

Aspinal holes nearly circular, with flat radially striated margin. Four aspinal pores of each hole rounded equilateral triangular. Porules of the shell simple, without ring and dimple. Four edges of the spines smooth.

Dimensions.—Diameter of the shell 0.4 to 0.5, of the central capsule 0.3 to 0.4.

Habitat.—North Atlantic, Færöe Channel (Gulf Stream), 1880, John Murray, surface.

2. Sphærocapsa dentata, n. sp. (Pl. 135, fig. 9).

Aspinal holes four-lobed, with broad concave margin denticulated on the periphery. Four aspinal pores of each hole pear-shaped, oblong, elevated in the centre. Porules of the shell simple, without ring and dimple. Four edges of the spines denticulate.

Dimensions.—Diameter of the shell 0.3 to 0.4, of the central capsule 0.2 to 0.3.

Habitat.—South Atlantic, Station 332, depth 2200 fathoms.

3. Sphærocapsa quadrata, n. sp. (Pl. 135, fig. 8).

Aspinal holes square, with concave umbilicus in the centre, surrounded by a convex denticulated margin. Four aspinal pores of each hole nearly square. Shell-porules with a polygonal elevated smooth ring, in the bottom of a shallow dimple. Four edges of the spines smooth.

Dimensions.—Diameter of the shell 0.22, of the central capsule 0.17.

Habitat.—Indian Ocean, south of Australia, Station 159, surface.

4. Sphærocapsa pavimentata, n. sp. (Pl. 135, fig. 10).

Aspinal holes four-lobed, with broad concave, irregularly crenated and figured margin. Four aspinal pores of each hole violin-shaped. Porules of the shell surrounded by an irregularly oblong ring with thick elevated, elegantly crenated margin. Four edges of the spines smooth.

Dimensions.—Diameter of the shell 0.36, of the central capsule 0.3.

Habitat.—South-east Pacific (off Valparaiso), Station 298, surface.

Genus 345. Astrocapsa,^[385] n. gen.

Definition.—Sphærocapsida with twenty radial spines longer than the radius of the shell, piercing its perspinal holes, with free external prolongation; therefore with four aspinal pores around each spine.

The genus Astrocapsa differs from the preceding Sphærocapsa in the external prolongation of the radial spines piercing the perspinal holes; it assumes therefore the common shape of the Dorataspida more than the other Sphærocapsida do.

1. Astrocapsa tritonis, n. sp.