Legion I. SPUMELLARIA, (continued 15)

Subgenus 1. Rhopalodictya, Haeckel.

Definition.—Triangular shell regular, with three arms of equal size and equidistant.

1. Rhopalodictyum abyssorum, Ehrenberg.

Rhopalodictyum abyssorum, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 299, Taf. viii. fig. 17.

Arms of equal size and equidistant, club-shaped, about as long as the diameter of the triangular central disk, and a little longer than the breadth of the pear-shaped rounded distal end. Surface rough.

Dimensions.—Radius of the arms 0.11, basal breadth 0.03, distal breadth 0.06.

Habitat.—Cosmopolitan; Atlantic, Indian, Pacific; tropical zone, surface.

2. Rhopalodictyum truncatum, Ehrenberg.

Rhopalodictyum truncatum, Ehrenberg, 1861, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 301.

? Dictyastrum angulatum, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 289, Taf. viii. fig. 18.

Arms of equal size and equidistant, nearly square, with straight edges, towards the truncated end a little broader, about of the same diameter as the central triangular disk. This species is indicated by Ehrenberg only by the short diagnosis, "Radiis stellæ tribus apice truncatis." It is probably identical with his figure of Dictyastrum angulatum (loc. cit.). This latter name I have retained for the similar Porodiscid (above, p. 526), mainly because the genera Dictyastrum and Rhopalodictyum, according to the insufficient diagnosis of Ehrenberg, seem to be identical. (Compare my Monograph, 1862, p. 466.)

Dimensions.—Radius of each arm 0.13, basal breadth 0.09, distal breadth 0.1.

Habitat.—Tropical Pacific, Philippine Sea, Station 200, depth 250 fathoms; Atlantic (Mexican Gulf Stream).

3. Rhopalodictyum subacutum, Ehrenberg.

Rhopalodictyum subacutum, Ehrenberg, 1861, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 301.

Arms of equal size and equidistant, club-shaped, three times as long as the diameter of the central disk, which equals the breadth of the thickened distal end; the latter is armed with a strong pyramidal terminal spine. (The diagnosis of Ehrenberg is "Radiis stellæ tribus, apice cuneatis subacutis.")

Dimensions.—Radius of the arms 0.2, basal breadth 0.04, distal breadth 0.07.

Habitat.—North Atlantic, surface and various depths; Greenland; Mexican Gulf Stream; Færöe Channel (John Murray).

4. Rhopalodictyum bifidum, n. sp.

Arms of equal size and equidistant, in the distal half forked, twice as long as the diameter of the central disk; both fork branches half as broad as the simple basal part, truncated at the distal end.

Dimensions.—Radius of the arms 0.16, basal breadth 0.08, distal breadth 0.04.

Habitat.—North Pacific, Station 237, surface.

Subgenus 2. Triactinosphæra, Dunikowski, 1882, Denkschr. d. k. Akad. d.

Definition.—Triangular shell bilateral or irregular, with three arms of different size or distance.

5. Rhopalodictyum zittelii, Haeckel.

Triactinosphæra zittelii, Dunikowski, 1882, Denkschr. d. k. Akad. d. Wiss, Wien, vol. 45, ii. p. 192.

Arms of different size and at unequal distances, one odd arm being a little shorter than the two paired arms; the odd angle between the latter is larger than the paired angles between them and the former. Arms club-shaped, their basal semi-cylindrical, half as broad as the spherical distal half, which bears a strong, conical, terminal spine. The discoverer of this remarkable, very old, Liassic species, Dunikowski, supposes that it is not a true Discoid, from the absence of a central disk; in my opinion the central disk (nearly spherical) has the same relation to the arms as in many other Discoidea, their equatorial plane is the same.

Dimensions.—Radius of the odd arm 0.18, of the paired arms 0.24; basal breadth 0.08, distal breadth 0.16.

Habitat.—Fossil in the Alpine Lias, Schafberg, near Salzburg, Dunikowski.

6. Rhopalodictyum elongatum, n. sp.

Arms of different size and at unequal distances, one odd arm being twice as long as both paired arms; the odd angle between the latter much larger than both equal paired angles. Arms nearly cylindrical, little flattened, three to six times as long as broad, with rounded blunt distal end.

Dimensions.—Radius of the arms 0.15 to 0.3, breadth 0.05.

Habitat.—Pacific, central area, Station 274, surface.

7. Rhopalodictyum curvatum, n. sp.

Arms of different size and at unequal distances, irregular, more or less curved, nearly cylindrical, five to ten times as long as broad, with rounded blunt distal end. (There were observed only two specimens of this remarkable irregular species; in one specimen all three arms were simple, in the other one odd arm forked. The length of the arms and the size of the angles between them seems to be very different and variable.)

Dimensions.—Radius of the arms 0.3 to 0.6 to 1.15, breadth 0.06 to 0.12.

Habitat.—Pacific, central area, Station 271, surface.

Genus 263. Dictyocoryne,^[302] Ehrenberg, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 830.

Definition.—Spongodiscida with three spongy arms on the margin of the circular or triangular disk, connected by a spongy patagium of different texture.

The genus Dictyocoryne differs from the foregoing Rhopalodictyum only in the patagium, connecting the three spongy arms, and bears to it the same relation as in the Porodiscida Euchitonia does to Rhopalastrum. The typical species of this genus is Dictyocoryne profunda, the only species figured by Ehrenberg. After his insufficient diagnosis Dictyocoryne was identical with his Spongaster (compare my Monograph, p. 467); but as the type of this latter genus (Spongaster tetras) figured by him, 1872, had four crossed arms, we retain this genus here separate.

Subgenus 1. Dictyocorynula, Haeckel.

Definition.—Triangular shell regular, with three arms of equal size and equal distance.

1. Dictyocoryne profunda, Ehrenberg.

Dictyocoryne profunda, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 307, Taf. vii. fig. 23.

Arms of equal size and equidistant, club-shaped, in the outer circular half three times as broad as in the inner cylindrical half, and much larger than the small triangular central disk. Patagium complete, forming an equilateral triangle with rounded corners.

Dimensions.—Radius of the arms 0.14, basal breadth 0.025, distal breadth 0.07.

Habitat.—Pacific, Philippine Sea, depth 3300 fathoms, Ehrenberg; Station 198, depth 2150 fathoms; Station 274, depth 2750 fathoms.

2. Dictyocoryne tetradiscus, n. sp.

Arms of equal size and equidistant, club-shaped, their outer circular half is quite as large as the circular central disk, and is connected with it by the thin cylindrical inner half, which is scarcely one-fourth as broad. Patagium complete, forming an equilateral triangle with rounded corners and convex sides.

Dimensions.—Radius of the arms 0.16, basal breadth 0.02, distal breadth 0.08.

Habitat.—Pacific, central area, Stations 271 to 274, in 2350 to 2750 fathoms.

3. Dictyocoryne euchitonia, Haeckel.

Dictyocoryne euchitonia, Haeckel, 1862, Monogr. d. Radiol., p. 468.

Arms of equal size and equidistant, lanceolate, twice as long as broad in the distal part, and three times as long as the small circular central disk. Patagium complete, forming an equilateral triangle with pointed corners. (Very similar to Euchitonia köllikeri, Monograph, 1862, p. 511, Taf. xxxi. fig. 6, but quite spongy, not concentric.)

Dimensions.—Radius of the arms 0.15, basal breadth 0.03, distal breadth 0.06.

Habitat.—Mediterranean (Messina), Haeckel.

4. Dictyocoryne trigona, n. sp.

Arms of equal size and equidistant, lanceolate, three times as long as broad in the middle part, and as the diameter of the triangular central disk; their distal end armed with a strong conical radial spine. Patagium complete, forming an equilateral triangle with pointed corners.

Dimensions.—Radius of the arms 0.2, basal breadth 0.02, distal breadth 0.06.

Habitat.—North Atlantic, Canary Islands, surface.

Subgenus 2. Dictyocorynium, Haeckel.

Definition.—Triangular shell bilateral or irregular, with three arms of different sizes or at different distances.

5. Dictyocoryne charybdaea, Haeckel.

Spongocyclia charybdaea, Haeckel, 1862, Monogr. d. Radiol., p. 472, Taf. xxviii. figs. 5, 6.

Spongodiscus charybdaeus, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 844.

Arms at different distances, nearly equilateral triangular, scarcely half as long as the radius of the large circular central disk. Both paired arms touching at their bases, separated by a great distance from the opposite odd arm. Patagium complete, nearly pentagonal. (The illustration in my Monograph, in the coloured plate xxviii., is better than my description, as I had not exactly separated the arms from the patagium.)

Dimensions.—Radius of the arms 0.18, basal breadth 0.08.

Habitat.—Mediterranean (Messina), surface.

6. Dictyocoryne pentagona, Stöhr.

Dictyocoryne pentagona, Stöhr, 1880, Palæontogr., vol. xxvi. p. 118, Taf. vii. fig. 2.

Arms at different distances, club-shaped, little longer than broad at their rounded distal end. Both paired arms smaller and more approximate than the opposite odd arm. Patagium complete, very large, enveloping the whole shell, and forming a pentagon with rectilinear base and transverse constriction, and with five rounded corners.

Dimensions.—Radius of the arms 0.1 to 0.15, middle breadth 0.04.

Habitat.—Fossil in the Tertiary rocks of Sicily, Grotte, Stöhr.

7. Dictyocoryne agrigentina, Stöhr.

Dictyocoryne agrigentina, Stöhr, 1880, Palæontogr., vol. xxvi. p. 118, Taf. vii. fig. 1.

Arms at different distances, club-shaped, about twice as long as broad, and smaller than the large triangular central disk. Both paired arms smaller and more approximate than the opposite odd arm. Patagium incomplete, enveloping only the basal half of the arms as a circular spongy disk of loose framework.

Dimensions.—Radius of the arms 0.18, basal breadth 0.05, distal breadth 0.08.

Habitat.—Fossil in the Tertiary rocks of Sicily, Grotte, Stöhr.

8. Dictyocoryne echinata, n. sp.

Arms unequal and at different distances, club-shaped, in the distal half twice as broad as in the basal half, three times as long as the small triangular central disk, at their distal end armed with one larger and several smaller conical spines. Both paired arms with touching bases, and only half as large as the doubly remote odd arm. Patagium incomplete, enveloping only the basal half of the arms, and forming a circular disk of looser framework. Surface thorny.

Dimensions.—Radius of the arms 0.15 to 0.2, basal breadth 0.03, distal breadth 0.06.

Habitat.—South Atlantic, Station 325, surface.

Genus 264. Spongasteriscus,^[303] Haeckel, 1862, Monogr. d. Radiol., p. 474 (sensu restricto).

Definition.—Spongodiscida with four spongy arms on the margin of the circular or quadrangular disk, crossed in two equatorial diameters, without a connecting patagium.

The genus Spongasteriscus (in the restricted definition here stated) exhibits on the margin of the disk four spongy arms, which form either a regular or a bilateral cross. It corresponds to Stauralastrum and Myelastrum among the Porodiscida, to Astractura among the Coccodiscida.

Subgenus 1. Spongasteriscinus, Haeckel.

Definition.—Cross formed by the four arms regular, rectangular, with equal-sized and equidistant arms.

1. Spongasteriscus ovatus, n. sp.

Arms at equal distances, forming a regular, rectangular cross, egg-shaped, with a broader rounded distal end, one and a third times as long as broad, and three times as long as the radius of the central disk; in the latter three to four concentric rings.

Dimensions.—Radius of the arms 0.1, greatest breadth 0.06.

Habitat.—Western Tropical Pacific, Station 225.

2. Spongasteriscus clavatus, n. sp.

Arms at equal distances, forming a regular, rectangular cross, club-shaped, about as long as the diameter of the central disk, and at their rounded distal end one and a third times as long as broad, at their narrow base only one third as broad. In the centre five to six concentric rings.

Dimensions.—Radius of the arms 0.13, distal breadth 0.06, basal breadth 0.02.

Habitat.—Pacific, central area. Station 271, surface.

3. Spongasteriscus mucronatus, n. sp.

Arms at equal distances, forming a regular, rectangular cross, club-shaped, three times as long as the radius of the central disk, in the distal half nearly circular, three to four times as broad as at the narrow base. The rounded distal end armed with a strong pyramidal spine. In the centre no concentric rings. (Similar to Stauralastrum rhopalophorum, Pl. 45, fig. 1, but quite spongy.)

Dimensions.—Radius of the arms 0.12, basal breadth 0.03, distal breadth 0.02.

Habitat.—Pacific, central area, Station 265, depth 2900 fathoms.

4. Spongasteriscus furcatus, n. sp.

Arms at equal distances, forming a regular, rectangular cross, in the distal third forked; both fork branches half as long as the basal undivided part of the arm, which is twice as long as broad. Distal ends of the eight branches blunt, rounded. In the central disk no concentric rings.

Dimensions.—Radius of the arms 0.12, basal breadth 0.03; distal breadth of the branches 0.02.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

5. Spongasteriscus armatus, n. sp.

Arms at equal distances, forming a rectangular, regular cross, in the distal half forked; both fork branches of the same length as the basal undivided part of the arm, which is nearly square. Distal ends of the eight branches armed with a strong pyramidal spine. In the central disk no concentric rings. (Similar to Dicranastrum cornutum, Pl. 45, fig. 2, but quite spongy.)

Dimensions.—Radius of the arms 0.18, basal breadth 0.03, distal breadth 0.015.

Habitat.—South Pacific, Station 295, depth 1500 fathoms.

Subgenus 2. Spongasterisculus, Haeckel.

Definition.—Cross formed by the four arms, bilateral or irregular, with the arms at different distances.

6. Spongasteriscus quadricornis, Haeckel.

Spongasteriscus quadricornis, Haeckel, 1862, Monogr. d. Radiol., p. 474, Taf. xxviii. figs. 8-10.

Spongodiscus quadricornis, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 844.

Arms at different distances, forming a bilateral or irregular cross, grouped in two opposite pairs; their form equilateral triangular; their length smaller than the radius of the large circular central disk, which exhibits in the interior eight to sixteen concentric rings.

Dimensions.—Radius of the arms 0.2, of the central disk 0.13; basal breadth of the arms 0.08.

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

7. Spongasteriscus tetraceros, Haeckel.

Spongasteriscus tetraceros, Haeckel, 1862, Monogr. d. Radiol., p. 475.

Arms at different distances, forming a bilateral or irregular cross, grouped in two opposite pairs; their form isosceles triangular; their length larger than the radius of the large elliptical central disk, which exhibits in the interior six to twelve concentric rings.

Dimensions.—Radius of the arms 0.16, of the central disk 0.1; basal breadth of the arms 0.06.

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

8. Spongasteriscus myelastrum, n. sp.

Arms at different distances, forming a bilateral or irregular cross, grouped in two opposite pairs; the arms of one pair broader and shorter than the arms of the other pair. Each arm in its basal half simple, in the distal half forked; ends of the fork branches blunt. In the central disk no concentric rings. (Similar to Myelastrum octocorne, Pl. 47, fig. 12, but quite spongy.)

Dimensions.—Radius of the arms 0.2, basal breadth 0.05, distal breadth 0.02.

Habitat.—North Pacific, Station 236, surface.

Genus 265. Spongaster,^[304] Ehrenberg, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 833.

Definition.—Spongodiscida with four spongy arms on the margin of the circular or quadrangular disk, connected by a spongy patagium of different texture.

The genus Spongaster differs from the foregoing Spongasteriscus in the patagium connecting the spongy arms, and bears therefore to it the same relation as, in the Porodiscida, Histiastrum does to Stauralastrum, or, in the Coccodiscida, Stauractura does to Astractura. The typical specimen, figured by Ehrenberg (Spongaster tetras), exhibits a regular, square disk, as also some other species. In a certain number of other species (formerly united by me with Spongocyclia) the quadrangular disk is bilateral.

Subgenus 1. Spongastrella, Haeckel.

Definition.—Cross formed by the four arms regular, rectangular, with the arms of equal size and equidistant.

1. Spongaster tetras, Ehrenberg.

Spongaster tetras, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 299, Taf. vi. (iii.) fig. 8.

Dictyocoryne tetras, Haeckel, 1862, Monogr. d. Radiol., p. 469.

Arms at equal distances, forming a rectangular, regular Myelastrum, papiliocross, club-shaped, about twice as long as the diameter of the square central disk and eight times as long as broad at their base. Distal ends rounded, perfectly enclosed by the complete patagium, which forms a regular square, with slightly concave sides.

Dimensions.—Radius of the arms 0.12, distal breadth 0.03, basal breadth 0.015; length of the square side 0.2.

Habitat.—Cosmopolitan; Atlantic, Indian, Pacific, surface and in various depths.

2. Spongaster quadratus, n. sp.

Arms at equal distances, forming a regular, rectangular cross, club-shaped, about four times as long as the diameter of the central circular disk, and five times as long as broad at the base. Basal third of the arms square; distal two thirds triangular, three times as broad, with a truncated distal end. Patagium complete, perfectly enveloping the arms, and bordered by an elegant, radially striated, broad edge, forming a regular square. (Similar to Histiastrum quadratum, Pl. 46, fig. 4, but quite spongy.)

Dimensions.—Radius of the arms 0.15, distal breadth 0.06, basal breadth 0.02; length of the square side 0.25.

Habitat.—Pacific, central area, Stations 270 to 274, depths 2350 to 2925 fathoms.

3. Spongaster cruciatus, n. sp.

Arms at equal distances, forming a rectangular, regular cross, lanceolate, three times as long as broad and as the diameter of the central circular disk. Ends of the arms provided with a short conical spine. Patagium incomplete, enveloping only the basal half of the arms, forming a regular square with concave sides.

Dimensions.—Radius of the arms 0.18, greatest breadth 0.05; length of the square side 0.2.

Habitat.—South Pacific, Station 288, surface.

4. Spongaster pentacyclus, n. sp.

Arms at equal distances, forming a rectangular, regular cross, of the same size and form as the circular central disk, so that the dark interior part of the shell is composed of five equal circular disks, situated in a quincuncial manner. The clearer complete patagium, enveloping the whole cross perfectly, forms a regular square with rounded edges.

Dimensions.—Radius of the arms 0.2; diameter of each of the five circular disks 0.01; length of the square side 0.35.

Habitat.—West Indies, Cuba, surface (Thomson).

Subgenus 2. Spongastromma, Haeckel.

Definition.—Cross formed by the four arms bilateral or irregular, with the arms at different distances.

5. Spongaster orthogonus, Haeckel.

Spongocyclia orthogona, Haeckel, 1862, Monogr. d. Radiol., p. 471, Taf. xxviii. fig. 3.

Spongodiscus orthogonus, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 844.

Arms at different distances, forming a bilateral cross, grouped in two opposite pairs of equal size and similar form. Arms club-shaped, about as long as the diameter of the central circular disk, enveloped perfectly by the complete patagium, which forms a regular rectangle, the longer side of which is one and a half times as long as the shorter side. (The arms in my figure are not distinctly enough marked.)

Dimensions.—Radius of the arms 0.08, breadth 0.02; length of the larger side of the rectangle 0.15, of the smaller 0.1.

Habitat.—Mediterranean (Messina), surface.

6. Spongaster scyllaeus, Haeckel.

Spongocyclia scyllaea, Haeckel, 1862, Monogr. d. Radiol., p. 471, Taf. xxviii. fig. 4.

Spongodiscus scyllaeus, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 844.

Arms at different distances, forming a bilateral cross, grouped in two opposite pairs of different size and form, one pair smaller and less divergent than the other. Arms club-shaped, little longer than the radius of the central circular disk, enveloped perfectly by the complete patagium, which forms a trapezium; the convergent longer sides of the latter are one and a half times as long as the larger, and twice as long as the smaller parallel side. (The arms are in my figure, loc. cit., not distinctly enough marked.)

Dimensions.—Radius of the arms 0.12 to 0.14, breadth 0.02; length of both convergent sides 0.24, of the larger parallel side 0.18, of the smaller 0.12.

Habitat.—Pacific, central area, Station 272, surface; Mediterranean (Messina).

Suborder VI. LARCOIDEA, Haeckel, 1883 (Pls. 9, 10, 49, 50).

Definition.—Spumellaria with lentelliptical central capsule (rarely somewhat modified or allomorphic), with a lentelliptical fenestrated siliceous shell (often modified or allomorphic, and sometimes quite irregular). Growth different in the three unequal dimensive axes, perpendicular one to another. The typical Lentellipsis is characterised by three elliptical dimensive planes of different sizes, perpendicular one to another.

The section Larcoidea, the fourth and last of the Sphærellaria, comprises all those forms of this group in which the fenestrated shell originally is lentelliptical, characterised by different growth in three different axes, perpendicular one to another, all three equal on both poles. The geometrical fundamental form of the shell is therefore a lentellipsis or a triaxial ellipsoid; and this typical form is preserved completely in the majority of Larcoidea in the pure geometrical form of the central capsule.

The three dimensive axes, which determine the typical form of Larcoidea, are commonly differentiated in such a way, that the first, the longitudinal or principal axis, is the longest; both its poles, oral and aboral (or anterior and posterior) are equal. The second, the lateral or transverse axis, is commonly less than the first, greater than the third axis; both its poles are the equal lateral poles (right and left not differentiated). The third dimensive axis, the equatorial or sagittal axis, is commonly the shortest; both its equal poles are the sagittal poles (dorsal and ventral poles not different). The relative size of the three dimensive axes in the human body exhibits similar relations.

The three dimensive planes of the Larcoidea, the sagittal, lateral, and transverse planes, are elliptical, all three of different sizes. The first plane, the median or sagittal plane, is commonly as regards size between the two others; its major axis is the principal, its minor the sagittal axis; it separates the right half of the body from the left. The second plane or lateral plane, is commonly larger than the two others; its major axis the principal, its minor the transverse axis; it separates the dorsal half of the body from the ventral. The third plane, the equatorial or zonal plane, is commonly less than the two others; its major axis the lateral, its minor the sagittal axis; it separates the two principal halves of the body, the oral and aboral halves.

In my Monograph (1862) only very few forms of Larcoidea are described, Tetrapyle and Lithelius (the latter representing a peculiar family, Lithelida). In my Prodromus (1881, pp. 463, 464) I disposed all observed forms of Larcoidea in two different families, the Pylonida and Lithelida. The rich materials of the Challenger collection have since offered an astonishing number of new and interesting forms of this section, so that I can enumerate here fifty-one genera and two hundred and sixty-five species. I dispose them here in four subsections and nine families. Three of these have regular lentelliptical shells, which are not articulate, and without annular constrictions (Larcarida, Larnacida, Pylonida); these form the subsection Pylolarcida. Two other families (Tholonida and Zonarida) are distinguished by annular constrictions, which divide the regular lentelliptical shell into a number of dome-shaped chambers or cupolas; we call these Thololarcida. A third group, Spirolarcida, comprises the Larcoidea with spiral growth; the two families of Lithelida and Streblemida. Finally a fourth group the Sorolarcida is formed by the Larcoidea with irregular shells, also two families, the Phorticida and Soreumida.

The first family of Larcoidea, the Larcarida, contains the most simple forms, beginning with Cenolarcus, a quite simple lentelliptical latticed shell. In Coccolarcus we find already two concentric shells, connected by radial beams, an inner medullary and an outer cortical shell. In Spongolarcus the lentelliptical shell becomes spongy.

The second family, Larnacida, is very similar to the Larcarida, and seems to diverge only by the different mode of connection between the two concentric lentelliptical shells. But in truth this slight difference is of great morphological importance, as it depends on a quite different and peculiar mode of growth. In the foregoing Larcarida (Coccolarcus, &c.), the concentric shells originate in the same manner as in the concentric Prunoidea and Sphæroidea, by radial beams, which arise from the surface of the inner (medullary) shell and become connected by a network to form the outer (cortical) shell. Here, in the Larnacida, a quite similar shell originates in a quite different way, first arrived at in the Pylonida (Trizonium). Both concentric shells become here connected by peculiar lattice girdles, which are developed in the perimeter of the three elliptical dimensive planes. Firstly, on both sides of a simple, spherical, or lentelliptical central chamber, arise two lateral wings (on the poles of the transverse axis), and build around the former a transverse girdle. This is crossed by a larger lateral girdle, the minor axis of which is the major of the former, and perpendicular to both girdles is yet developed a third, the sagittal girdle. If the open fissures or "gates" between these three girdles become closed by network, we obtain Larnacilla, the probable ancestral form of all Larnacida.

Whilst in Larnacilla and Larnacidium this typical trizonal lentelliptical shell constitutes by itself alone the whole skeleton, in the other Larnacida it becomes overgrown by outer envelops, and so becomes enclosed in the interior of the central capsule as a "Larnacilla-shaped medullary shell." If the enclosing external envelops be simply latticed, we get the subfamily Larnacalpida; if they be spongy, we get the Larnacospongida.

The third family, Pylonida, is the most important of all Larcoidea, as not only the largest and most interesting number of species belong to it, but also many other genera (far the greater part of all Larcoidea) may be derived from it. The peculiar character of the Pylonida is determined by the imperfect fenestration of the lentelliptical shell growing in the three dimensive axes in a quite different manner. Each elliptical dimensive plane becomes circumscribed by an elliptical latticed girdle (or fenestrated ring), and between these three girdles (perpendicular one to another) remain wide open fissures of the shell or "gates" (Pylæ). The beginning of the shell-building is the same as in Larnacilla, the most simple form of Larnacida. From a quite simple medullary shell, a spherical, subspherical, ellipsoidal, or lentelliptical central chamber, arise two latticed wings, opposite on the poles of the transverse axis (Monozonium). Both wings are short and wide hollow fenestrated tubes, the axes of which are parallel to the principal axis. Therefore they form together with the central chamber an elliptical transverse girdle. This first girdle becomes crossed by a second lateral girdle; from both poles of the transverse axis arise latticed wings, which unite on the poles of the principal axis, therefore the minor axis of this second larger ring is the major axis of the first smaller ring (Dizonium). Between the two crossed rings remain four wide open gates. Now follows the development of a third sagittal girdle, arising from both poles of the principal axis and overgrowing the four gates. But as this third girdle is larger than the second, four other larger gates arise between the two (in planes perpendicular to the former four gates). Now we have the characteristic and most important trizonal shell (Trizonium), composed of three elliptical lattice-girdles of different size, perpendicular one to another, and enclosing a simple central chamber. If the four gates of this Trizonium become closed by lattice-work, it passes over into Larnacilla, the most important ancestral form of the Larnacida.

This most significant "trizonal shell," either incompletely latticed in Trizonium (with four open gates), or completely latticed by fenestration of the four gates, in Larnacilla, is to be found in far the greater part of all Larcoidea, representing the medullary shell, which is overgrown by an outer cortical shell. In many Larcoidea, in which this "Larnacilla-shell" is absent, it is perhaps lost by phylogenetic reduction, or retrograde metamorphosis.

The same process of triple girdle-building, by which the typical Trizonium-shell or Larnacilla-shell is produced (Haplozonaria), is repeated once or twice in the larger forms of Pylonida. The first system of three girdles (perpendicular one to another) becomes overgrown by a second system of the same formulation in the Diplozonaria, and this becomes overgrown by a third system in the Triplozonaria; in the highest genus of this group, Pylozonium, we find not less than nine girdles (three systems, each of three girdles). Till now only one genus of the whole polymorphous family was well known, Tetrapyle (with five girdles, three of the medullary, two of the cortical shell). If the gates between the girdles remain open, all these forms must be regarded as Pylonida; if the gates afterwards become closed by a network, they pass over into other families.

The fourth family of the Larcoidea is the Tholonida, distinguished by the polythalamous shell being composed of a certain number of roundish or hemispherical chambers (domes or cupolas), which surround a primordial central chamber in quite regular disposition, lying opposite in pairs on the poles of the three dimensive axes. If we imagine that each "wing" (or open half-girdle) of the Pylonida becomes closed by a lattice-work, and so transformed into a hemispherical or roundish cupola, we obtain the characteristic shell of the Tholonida. Indeed every girdle of the former corresponds to a pair of opposite domes of the latter. The axis of each pair of domes is one of the three dimensive axes.

The primordial chamber of the Tholonida (or the central chamber, around which all cupolas are regularly disposed) is either a simple lentelliptical lattice-shell, like Cenolarcus, or it is a trizonal shell (with an enclosed concentric medullary shell), like Larnacilla. As in both cases the building and the disposition of the cupolas around it are quite the same, we can suppose that the whole family of Tholonida may have been derived originally from Larnacilla (or Trizonium), and that the Cenotholida (with a simple central chamber) are sprung from the Coccotholida (with a Larnacilla-shaped central chamber) by reduction and loss of the original medullary shell.

The family Tholonida can be divided into three subfamilies according to the disposition of the cupola-pairs in one, two, or three dimensive axes. In the Cubotholida lie two cupolas on the poles of the transverse axis of the central chamber (corresponding to Amphipyle); in the Staurotholida we find four cupolas crosswise disposed, on the poles of the transverse and principal axes (corresponding to Tetrapyle); in the Cubotholida are at least six cupolas, on the poles of all three dimensive axes (corresponding to Tholonium). In all three cases the number of cupolas may be augmented by the secondary apposition of other chambers or domes in the same disposition. Sometimes also the whole cortical shell becomes enclosed by an external veil or mantle of delicate network. The lentelliptical (or often nearly cubical) central chamber becomes often reduced, so that its sides are incompletely latticed or widely opened; in some Cubotholida only the twelve edges of the eight cornered cubical central chamber remain; its six sides are quite open and only over-vaulted by the six hemispherical cupolas. From the opposite points of the latter (in the deep annular constrictions between them) often arise radial spines, and these lie commonly in diagonal planes, separating the dome-pairs.

A similar dome-building or a composition of the polythalamous shell by pairs of cupolas we find also in the next (fifth) family, the Zonarida. But here the true cause of the peculiar dome-structure is quite different, not an apposition of new chambers, but the constriction of a cortical shell-like Larnacalpis by two or more constrictions. These constrictions lie in dimensive planes (or in planes parallel to these), and therefore the cupolas are (all or partly) in diagonal planes, a condition quite opposite to that found in the Tholonida. One of the annular constrictions is constantly in the sagittal plane (separating the right and left halves of the shell). The number of the constrictions in the few genera is two, three, and four, and therefore the number of the cupolas four, six, or eight. As this cortical shell constantly encloses a trizonal medullary shell (or Larnacilla-shell), we cannot doubt that the Zonarida must be derived from the Larnacida.

Whilst in all the foregoing five families of Larcoidea the shell-form is regular and their geometrical fundamental form is a lentellipsis (or a triaxial ellipsoid, with three unequal isopolar dimensive axes), in the four remaining families of this suborder the shell becomes bilateral or irregular (with the poles of the axes unequal). In two of these families (Lithelida and Streblemida) the growth of the shell becomes spiral, in the last two families (Soreumida and Phorticida) quite irregular. But as in all four families we encounter the typical trizonal medullary shell (or Larnacilla-shell), we are convinced that they must be derived (wholly or partially) from the Larnacida.

The Lithelida (the sixth family) are Larcoidea with spiral growth and bilateral form (like Nautilus); therefore the spiral line lies in one plane and this spiral plane divides the whole shell into two symmetrical halves (right and left). The axis of the spiral (around which the shell winds) is a straight line, one of the three dimensive axes. In the greater part of Lithelida (in the Larcospirida) the primordial of central chamber of the polythalamous shell is a trizonal medullary shell or Larnacilla-shell, and the growth of the first spiral turning begins as the development of the first (transverse) cortical girdle of Amphipyle; but as one wing (or lateral half) of this girdle grows more rapidly than the other, it overgrows the latter and begins the spiral winding; if the other wing follow and overgrow the first, the spiral becomes double. Each of the three dimensive girdles (of the Pylonida) may begin the spiral winding. There can be no doubt that all these Lithelida (the Larcospirida) must be derived from the Pylonida, by unequal growth of the two halves of one girdle. Perhaps from these may also derived the other part of this family, the Spiremida (Spirema and Lithelius); in these the primordial chamber of the spiral shell is simple, and may be derived by reduction of the original Larnacilla-shell. But it is also possible that the Spiremida proceed directly from the Larcarida, and that their ancestors did not possess a Larnacilla-shell.

The Streblemida (the seventh family) are Larcoidea with spiral growth and asymmetrical form of the polythalamous shell (like Helix or Turrilites); therefore the spiral line is twisted like a winding stair, and the spiral face is curved and divides the shell into two unequal halves. The Streblemida have the same likeness and relation to the turbinoid Foraminifera (Rotalia, Globigerina, &c.) as the Lithelida to the nautiloid Foraminifera (Polystomella, Nummulina, &c.). As in these calcareous Rhizopods also the peculiar growth of the siliceous Streblemida begins from a primordial chamber to which a variable number of roundish chambers (of increasing size) is apposed. But the building of these chambers and of their septa is by no means so regular and complete as in the greater number of turbinoid Foraminifera. As in a part of this family the primordial chamber is Larnacilla-shell, these also may be derived from the Larnacida, but the other part (with simple central chamber) is perhaps produced directly from the Larcarida.

The eighth family, Soreumida, is perhaps derived from the Streblemida by the loss of the spiral growth. The polythalamous shell is similar to the latter, but the chambers are aggregated without any order, like the Acervulinida among the Foraminifera. In some cases also here the primordial chamber is a trizonal Larnacilla-shell, in other cases it is a simple, subspherical or lentelliptical shell.

The last family, the Phorticida, is formed of irregular Larcoidea, in which a lentelliptical trizonal Larnacilla-shell (as an inner medullary shell) is enveloped by an irregular, latticed, or spongy cortical shell. They can be regarded as abnormalities or irregular deformities of Larnacida or Pylonida.

The central capsule of the Larcoidea is originally lentelliptical and preserves this form, the "triaxial ellipsoid," in the greater number of genera. In some groups it follows the prevalent growth of the shell in the direction of one of the three dimensive axes, and becomes prolonged in this way. In many chambered forms (particularly Tholonida and Zonarida) the growing central capsule gets constricted, corresponding to the constrictions of the shell. In the Soreumida and Phorticida its form often becomes irregular. But in general for the greater number of Larcoidea the lentelliptical form of their central capsule is quite characteristic.

Synopsis of the Families of Larcoidea.

Larcoidea with a regular or symmetrical shell, the growth of which is determined by the three dimensive axes. (Both poles of each axis are equal.) Cortical shell completely latticed, without external gates (or interzonal fissures), without annular constrictions and domes. Medullary shell absent or simple (spherical or lentelliptical), 1. Larcarida.

Medullary shell trizonal or Larnacilla-shaped (composed of three dimensive girdles), 2. Larnacida.

Cortical shell incompletely latticed, with two to four or more symmetrically disposed gates or fissures remaining between latticed dimensive girdles, 3. Pylonida.

Cortical shell completely latticed, without external gates (or interzonal fissures), with two or more annular constrictions, which separate three to six or more dome-shaped protuberances. Constrictions of the cortical shell in diagonal planes; domes in dimensive axes, 4. Tholonida.

Constrictions of the cortical shell in dimensive planes; domes in diagonal axes, 5. Zonarida.

Larcoidea with a symmetrical or irregular shell, either with spiral growth or with quite irregular growth. (Both poles of one axis are different.) Cortical shell with spiral growth. Spiral cortical shell bilateral (with plane spiral), 6. Lithelida.

Spiral cortical shell asymmetrical (with ascending spiral), 7. Streblemida.

Cortical shell with quite irregular growth. Cortical shell simple, with one single chamber, 8. Phorticida.

Cortical shell composed of a number of heaped up or aggregated chambers, 9. Soreumida.

Larcoidea with a regular or symmetrical shell, the growth of which is determined by the three dimensive axes. (Both poles of each axis are equal.)

Cortical shell completely latticed, without external gates (or interzonal fissures), without annular constrictions and domes.

Medullary shell absent or simple (spherical or lentelliptical),

1. Larcarida.

Medullary shell trizonal or Larnacilla-shaped (composed of three dimensive girdles),

2. Larnacida.

Cortical shell incompletely latticed, with two to four or more symmetrically disposed gates or fissures remaining between latticed dimensive girdles,

3. Pylonida.

Cortical shell completely latticed, without external gates (or interzonal fissures), with two or more annular constrictions, which separate three to six or more dome-shaped protuberances.

Constrictions of the cortical shell in diagonal planes; domes in dimensive axes,

4. Tholonida.

Constrictions of the cortical shell in dimensive planes; domes in diagonal axes,

5. Zonarida.

Larcoidea with a symmetrical or irregular shell, either with spiral growth or with quite irregular growth. (Both poles of one axis are different.)

Cortical shell with spiral growth.

Spiral cortical shell bilateral (with plane spiral),

6. Lithelida.

Spiral cortical shell asymmetrical (with ascending spiral),

7. Streblemida.

Cortical shell with quite irregular growth.

Cortical shell simple, with one single chamber,

8. Phorticida.

Cortical shell composed of a number of heaped up or aggregated chambers,

9. Soreumida.

Family XXIV. Larcarida, Haeckel, 1883 (Pl. 50, figs. 1, 2).

Definition.—Larcoidea with a regular, completely latticed, lentelliptical cortical shell, without open gates and annular constrictions; medullary shell absent or simple (not trizonal), connected with the cortical shell by radial beams.

The family Larcarida opens the long series of Larcoidea as the most simple group of this suborder. It commences with Cenolarcus, a quite simple lentelliptical latticed shell, which is characterised by three unequal isopolar dimensive axes, perpendicular one to another. The major of these three axes is the longitudinal or principal, the middle is the lateral or transverse, and the minor is the equatorial or sagittal axis (as in the human body). Among the three dimensive planes, which are determined by pairs of these axes, the lateral plane is the largest (halved by the crossed principal and lateral axes). The intermediate is the sagittal plane or median plane (halved by the crossed principal and sagittal axes). The smallest is the equatorial plane or transverse plane (halved by the crossed lateral and sagittal axes). Therefore the shell has all the characters of the true Lentellipsis or of the "triaxial ellipsoid," and its axes agree with the three axes of the "rhombic crystalline system."

In the three subfamilies of Larcarida this lentelliptical shell assumes a different shape: in the Cenolarcida it remains simple, in the Spongolarcida it becomes spongy (sometimes quite filled out with a spongy framework), in the Coccolarcida it is composed of two or more concentric lentelliptical shells (at least an inner medullary and one outer cortical shell). These shells are simply connected by radial beams, and not, as in the Larnacida, by latticed wings (or half girdles).

The network of the Larcarida shell is sometimes regular, commonly irregular (as in the greater number of Larcoidea). The surface of the shell is sometimes smooth or thorny, at other times covered with radial spines. These are often symmetrically disposed, either on the poles of the dimensive axes or in crossed diagonal planes.

The central capsule is a true "lentellipsis" in a geometrical sense; it is halved by three elliptical dimensive planes of different sizes, perpendicular one to another. In the Cenolarcida the central capsule lies freely inside the simple (cortical) shell, only separated from it by the jelly-mantle. In the Coccolarcida it contains the medullary shell, and is enclosed by the simple or double cortical shell, perforated by the radial beams connecting the two shells. The spongy shell of the Spongolarcida exhibits a different relation to the central capsule: in Spongolarcus the latter lies freely in the internal cavity of the spongy shell; in Stypolarcus, where this cavity is quite filled with a spongy network, the central capsule also contains a part of it.

The morphological and phylogenetic relations of the Larcarida to the other families of Spumellaria admit of a different explanation. As this family contains the most simple forms of all Larcoidea, we can regard the Cenolarcus as the common ancestral form of this group, having originated from Actilarcus (or the lentelliptical Actissa) by the building of a simple lentelliptical lattice-shell. But it is also possible that a part of the Larcarida (or all?) descend from Larnacida by reduction or loss of the original Larnacilla-shell (compare Cenolarcus triaxonius, p. 607).

Synopsis of the Genera of the Larcarida.

III. Subfamily Cenolarcida. Shell simple, latticed (lentelliptical cortical shell). Without radial spines, 266. Cenolarcus.

With radial spines, 267. Larcarium.

III. Subfamily Coccolarcida. Shell composed of two or more concentric latticed shells (inner medullary and outer cortical). Without radial spines, 268. Coccolarcus.

With radial spines, 269. Larcidium.

III. Subfamily Spongolarcida. Shell spongy, partly or whole composed of a spongy framework. With an internal cavity, 270. Spongolarcus.

Without an internal cavity, 271. Stypolarcus.

I. Subfamily Cenolarcida. Shell simple, latticed (lentelliptical cortical shell).

Without radial spines,

266. Cenolarcus.

With radial spines,

267. Larcarium.

II. Subfamily Coccolarcida. Shell composed of two or more concentric latticed shells (inner medullary and outer cortical).

Without radial spines,

268. Coccolarcus.

With radial spines,

269. Larcidium.

III. Subfamily Spongolarcida. Shell spongy, partly or whole composed of a spongy framework.

With an internal cavity,

270. Spongolarcus.

Without an internal cavity,

271. Stypolarcus.

Subfamily 1. Cenolarcida, Haeckel.

Definition.—Larcarida with a simple, lentelliptical latticed shell (cortical shell without a medullary shell).

Genus 266. Cenolarcus,^[305] n. gen.

Definition.—Larcarida with a simple, lentelliptical latticed shell, without a medullary shell, without radial spines.

The genus Cenolarcus begins the group of Larcoidea as the most simple form of this suborder. It corresponds to Cenosphæra among the Sphæroidea, to Cenodiscus among the Discoidea, to Cenellipsis among the Prunoidea. The simple latticed shell is distinguished from that of the three other genera by its typical lentelliptical form, a triaxial ellipsoid with three dimensive axes of unequal length. Probably Cenolarcus is the original ancestral form of the Larcoidea, derived from Actilarcus (the lentelliptical Actissa) by the formation of a simple fenestrated shell around the lentelliptical central capsule. But possibly also some species of Cenolarcus may be derived from Coccolarcus or Larnacilla by reduction and loss of the medullary shell (compare Cenolarcus triaxonius, n. sp.).

1. Cenolarcus primordialis, n. sp. (Pl. 50, figs. 7, 7a, 7b).

Network of the shell regular, with circular, hexagonally framed pores, twice as broad as the elevated bars; about ten pores on the half meridian, eight on the half equator. Surface a little rough. Proportion of the three dimensive axes = 2 : 2.5 : 3.

Dimensions.—Principal axis (or length) 0.12, transverse axis (or breadth) 0.1, sagittal axis (or thickness) 0.08; pores 0.01, bars 0.005.

Habitat.—Pacific, central area, Station 271, depth 2425 fathoms.

2. Cenolarcus dimensivus, n. sp.

Network of the shell regular, with circular pores (without hexagonal frames), three times as broad as the thin bars; about twelve pores on the half meridian, nine on the half equator. Surface thorny. Proportion of the three dimensive axes = 3 : 4 : 5.

Dimensions.—Principal axis 0.15, transverse axis 0.12, sagittal axis 0.09; pores 0.012, bars 0.004.

Habitat.—North Pacific, Station 244, surface.

3. Cenolarcus triaxonius, n. sp.

Network of the shell regular, with circular, hexagonally framed pores, four times as broad as the thin bars; about twelve pores on the half meridian, nine on the equator. Surface smooth. From the inner surface of the shell arise six very thin radial beams, opposite in pairs in the three dimensive axes; all six beams end freely in a little knob, at an equal distance from the centre; therefore this remarkable species seems to have lost a medullary shell (descending from Coccolarcus or Larnacilla?). Proportion of the three dimensive axes = 2 : 2.5 : 3.

Dimensions.—Principal axis 0.13, transverse axis 0.11, sagittal axis 0.09; pores 0.012, bars 0.03.

Habitat.—Tropical Atlantic, Station 338, depth 1990 fathoms.

4. Cenolarcus lentellipticus, n. sp.

Network of the shell regular, with circular pores of the same breadth as the thick bars; about eighteen pores on the half meridian, fourteen on the half equator. Surface smooth. Proportion of the three dimensive axes = 2 : 3 : 4.

Dimensions.—Principal axis 0.16, transverse axis 0.12, sagittal axis 0.08; pores and bars 0.004.

Habitat.—Western Tropical Pacific, Station 224, surface.

5. Cenolarcus minimus, n. sp.

Network of the shell subregular, with very small circular pores of the same breadth as the bars; only four pores on the half meridian, three on the half equator. Surface smooth. Proportion of the three dimensive axes = 3 : 4 : 5.

Dimensions.—Principal axis 0.05, transverse 0.04, sagittal axis 0.03; pores and bars 0.006.

Habitat.—Pacific, central area, Station 266, depth 2750 fathoms.

Genus 267. Larcarium,^[306] n. gen.

Definition.—Larcarida with a simple, lentelliptical latticed shell, without a medullary shell; surface covered with radial spines.

The genus Larcarium differs from Cenolarcus only in the possession of radial spines on the surface of the simple fenestrated lentelliptical shell. These spines are commonly disposed symmetrically, opposite in pairs, either on the poles of the three dimensive axes, or on the poles of certain diagonal axes. Larcarium differs from the similar genera Larcidium, Larnacidium, and Larnacantha by the absence of any medullary shell.

1. Larcarium amphistylum, n. sp.

Shell thorny, with two large conical spines, opposite on both poles of the principal axis, somewhat longer than it. Network of the shell regular, with circular, hexagonally framed pores, twice as broad as the bars; about twelve pores on the half meridian, ten on the half equator. Proportion of the three dimensive axes = 3 : 4 : 5.

Dimensions.—Principal axis (or length) 0.15, transverse axis (or breadth) 0.12, sagittal axis (or thickness) 0.09; pores 0.01, bars 0.005.

Habitat.—Pacific, central area, Station 274, depth 2750 fathoms.

2. Larcarium staurostylum, n. sp.

Shell smooth, with four short three-sided pyramidal spines of equal length, opposite in pairs on the poles of the principal and lateral axes. Network of the shell regular, with circular pores of the same breadth as the bars; about eight pores on the half meridian, six on the half equator. Proportion of the three dimensive axes = 2 : 2.5 : 3.

Dimensions.—Length of the shell 0.12, breadth 0.1, thickness 0.08; pores and bars 0.006.

Habitat.—South Pacific, Station 300, depth 1375 fathoms.

3. Larcarium hexastylum, n. sp.

Shell smooth, with six short conical spines of equal length (= the shortest axis of the shell), opposite in pairs on the poles of the three dimensive axes. Network of the shell subregular, with circular pores three times as broad as the bars; about eleven pores on the half meridian, nine on the half equator. Proportion of the three dimensive axes = 3 : 4 : 5.

Dimensions.—Length of the shell 0.1, breadth 0.08, thickness 0.06, pores 0.006; bars 0.002.

Habitat.—North Pacific, Station 244, surface.

4. Larcarium axostylum, n. sp.

Shell thorny, with six strong conical radial spines, opposite in pairs on the poles of the three dimensive axes. All three pairs are of different sizes, the length of each spine corresponding nearly to the size of the shell-axis, of which it is the prolongation. Network of the shell subregular, with circular pores twice as broad as the bars; ten on the half meridian, eight on the half equator. Proportion of the three dimensive axes = 2 : 3 : 4.

Dimensions.—Length of the shell 0.12, breadth 0.09, thickness 0.06; pores 0.01, bars 0.005.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

5. Larcarium octostylum, n. sp.

Shell thorny, with eight thin cylindrical radial spines, opposite in pairs in two crossed diagonal planes. Network of the shell irregular, with roundish pores, twice to four times as broad as the bars; nine to eleven on the half meridian, five to seven on the half equator. Proportion of the three dimensive axes = 3 : 4 : 5.

Dimensions.—Length of the shell 0.11, breadth 0.09, thickness 0.07; pores 0.006 to 0.012, bars 0.003.

Habitat.—Pacific, central area, Station 267, surface.

6. Larcarium polystylum, n. sp.

Shell thorny, with numerous (twenty to thirty) stronger conical radial spines, about as long as the shortest axis of the shell. Network of the shell irregular, with roundish pores, twice to four times as broad as the bars; seven to eight on the half meridian, five to six on the half equator. Proportion of the three dimensive axes = 1 : 2 : 3.

Dimensions.—Length of the shell 0.09, breadth 0.06, thickness 0.03; pores 0.006 to 0.012, bars 0.003.

Habitat.—South Atlantic, Station 323, surface.

7. Larcarium chætostylum, n. sp.

Shell bristly, with very numerous (sixty to eighty or more) very thin, bristle-like, radial spines, somewhat longer than the longest axis of the shell. Network irregular, with very small roundish pores, about the same size as the bars; sixteen to eighteen on the half meridian, thirteen to fifteen on the half equator. Proportion of the three dimensive axes = 1 : 1.5 : 2.

Dimensions.—Length of the shell (without spines) 0.13, breadth 0.1, thickness 0.07; pores and bars 0.004 to 0.006.

Habitat.—Pacific, central area, Station 273, surface.

Subfamily 2. Coccolarcida, Haeckel.

Definition.—Larcarida with encased lentelliptical shell, composed of two or more concentric lentelliptical latticed shells, which are united by radial beams (at least one inner medullary shell and one outer cortical shell).

Genus 268. Coccolarcus,^[307] n. gen.

Definition.—Larcarida with two concentric latticed shells, an outer lentelliptical cortical shell, and an inner (spherical or lentelliptical) medullary shell, both connected by radial beams. Surface without radial spines.

The genus Coccolarcus differs from Cenolarcus by the possession of an internal medullary shell. This is quite simple, either spherical or lentelliptical, and connected with the outer cortical shell by a number of radial beams. In the similar Larnacilla this connection is effected by four internal latticed lamellæ (the half lateral wings of the transverse girdle); therefore we find here four internal gates (on the poles of the principal axis), absent in Coccolarcus.

1. Coccolarcus lentellipsis, n. sp.

Cortical shell with smooth surface and regular network; pores circular, twice as broad as the bars; about thirteen on the half meridian, eleven on the half equator. Proportion of the three dimensive axes = 3 : 4 : 5. Medullary shell spherical, half as broad as the transverse radius.

Dimensions.—Principal axis (or length) of the cortical shell 0.15, transverse axis (or breadth) 0.12, sagittal axis (or thickness) 0.09; pores 0.01, bars 0.005; diameter of the medullary shell 0.03.

Habitat.—Pacific, central area, Station 272, depth 2600 fathoms.

2. Coccolarcus platellipsis, n. sp.

Cortical shell with thorny surface and irregular network; pores roundish, twice to three times as broad as the bars; sixteen to eighteen on the half meridian, ten to twelve on the half equator. Proportion of the three dimensive axes = 1 : 2 : 3. Medullary shell lentelliptical, one-third as large as the cortical shell.

Dimensions.—Length of the cortical shell 0.17, breadth 0.11, thickness 0.06; pores 0.008 to 0.012, bars 0.004; medullary shell 0.03 to 0.06.

Habitat.—Pacific, central area, Station 274, depth 2750 fathoms.

Genus 269. Larcidium,^[308] n. gen.

Definition.—Larcarida with two concentric latticed shells, an outer lentelliptical cortical shell, and an inner (spherical or lentelliptical) medullary shell, both connected by radial beams. Surface covered with radial spines.

The genus Larcidium differs from the foregoing Coccolarcus only in the possession of radial spines, and bears to it the same relation that Larcarium does to Cenolarcus. The spines are commonly symmetrically disposed, opposite in pairs in the dimensive axes, sometimes also in diagonal axes.

1. Larcidium dissacanthum, n. sp.

Cortical shell with thorny surface and regular network; pores circular, hexagonally framed, three times as broad as the bars; about thirteen on the half meridian, eleven on the half equator. Proportion of the three dimensive axes = 2 : 3 : 5. Medullary shell spherical, one-fourth as broad as the cortical, connected with it by two thin beams, lying in the principal axis, and prolonged on its poles into two strong conical spines, somewhat longer than the greatest axis.

Dimensions.—Length of the cortical shell (or principal axis) 0.15, breadth 0.09, thickness 0.07; pores 0.015, bars 0.005; medullary shell 0.025.

Habitat.—North Pacific, Station 253, depth 3125 fathoms.

2. Larcidium hexacanthum, n. sp.

Cortical shell with smooth surface and regular network; pores circular, twice as broad as the bars; about eleven on the half meridian, nine on the half equator. Proportion of the three axes = 2 : 2.5 : 3. Medullary shell spherical, one-third as broad as the cortical. On the surface six strong, three-sided pyramidal spines, all about as long as the breadth of the cortical shell.

Dimensions.—Length of the cortical shell 0.12, breadth 0.1, thickness 0.08; pores 0.01, bars 0.005; medullary shell 0.035.

Habitat.—Pacific, central area. Station 266, surface.

3. Larcidium axacanthum, n. sp.

Cortical shell with rough surface and irregular network; pores roundish, twice to four times as broad as the bars; about fifteen to nineteen on the half meridian, twelve to fourteen on the half equator. Proportion of the three axes = 2 : 3 : 4. Medullary shell lentelliptical, of the same form and structure as the cortical, but only one-third as large, connected with it by six thin radial beams, lying in pairs in the three dimensive axes; on the outside they are prolonged into six strong conical radial spines, which are in pairs of different size (as in Larcarium axostylum); the length of each spine nearly equals the axis of the cortical shell, of which it is the prolongation.

Dimensions.—Length of the cortical shell (and the principal spines) 0.18, breadth of it (and length of the lateral spines) 0.135, thickness of it (and length of the sagittal spines) 0.09; pores 0.005 to 0.013, bars 0.003.

Habitat.—Pacific, central area, Station 271, surface.

4. Larcidium octacanthum, n. sp.

Cortical shell thorny, with irregular network; pores roundish, once to four times as broad as the bars; about thirteen to fifteen on the half meridian, eleven to thirteen on the half equator. Proportion of the three axes = 1 : 2.5 : 4. Medullary shell lentelliptical, one-fifth as large as the cortical, connected with it by eight radial beams, which are situated in two crossed diagonal planes (opposite in pairs), and are prolonged on the surface into eight long and thin cylindrical radial spines similar to Tetrapyle octacantha.

Dimensions.—Length of the cortical shell 0.16, breadth 0.11, thickness 0.045; pores 0.003 to 0.012, bars 0.003; medullary shell 0.02 to 0.03.

Habitat.—Pacific, central area, Station 263, depth 2650 fathoms.

5. Larcidium dodecanthum, n. sp. (Pl. 50, figs. 8, 8a).

Cortical shell rough, with irregular network; pores roundish, twice to four times as broad as the bars; about twelve to fourteen on the half meridian, eight to ten on the half equator. Proportion of the three axes = 2 : 3 : 4. Medullary shell lentelliptical, one-third as large as the cortical, connected with it by twelve thin radial beams, which are prolonged outside into twelve strong conical radial spines, about half as long as the breadth of the shell.

Dimensions.—Length of the cortical shell 0.14, breadth 0.1, thickness 0.07; pores 0.008 to 0.015, bars 0.004; medullary shell 0.04 to 0.05.

Habitat.—South Pacific, Station 288, surface.

6. Larcidium polyacanthum, n. sp.

Cortical shell spiny, with irregular network; pores roundish, once to twice as broad as the bars; about ten to twelve on the half meridian, six to eight on the half equator. Proportion of the three axes = 1 : 2 : 3. Medullary shell lentelliptical, half as large as the cortical shell, connected with it by numerous (twenty to twenty-five) radial beams, which are prolonged outside into three-sided pyramidal spines, about as long as the breadth of the shell.

Dimensions.—Length of the cortical shell 0.18, breadth 0.12, thickness 0.06; pores 0.01 to 0.015, bars 0.008; medullary shell 0.03 to 0.09.

Habitat.—North Pacific, Station 244, depth 2900 fathoms.

Subfamily 3. Spongolarcida, Haeckel.

Definition.—Larcarida with spongy lentelliptical shell (with or without enclosed medullary shell).

Genus 270. Spongolarcus,^[309] n. gen.

Definition.—Larcarida with lentelliptical spongy shell, containing a central cavity of the same form, without medullary shell (without radial spines).

The genus Spongolarcus differs from Cenolarcus (its probable ancestral form) only in the development of spongy framework forming the wall of the hollow lentelliptical shell. It corresponds, therefore, to Plegmosphæra among the Sphæroidea, and to Spongellipsis among the Prunoidea. From these two similar spongy Sphærellaria it differs in its characteristic lentelliptical form, with three dimensive axes of unequal length.

1. Spongolarcus lentellipsis, n. sp.

Spongy network of the shell very loose, its meshes fifteen to twenty times as broad as the bars. Surface of the shell nearly smooth; diameter of its internal cavity twice as large as the thickness of its wall. Proportion of the three dimensive axes = 2 : 3 : 4.

Dimensions.—Length 0.16, breadth 0.12, height 0.08; thickness of the spongy wall 0.05.

Habitat.—Pacific, central area, Station 274, surface.

2. Spongolarcus triaxonius, n. sp.

Spongy network of the shell rather loose, its meshes twelve to sixteen times as broad as the bars. Surface of the shell rough; diameter of its internal cavity about eight times as large as the thickness of its wall. Proportion of the three dimensive axes = 2 : 2.5 : 3.

Dimensions.—Length 0.25, breadth 0.2, height 0.16; thickness of the spongy wall 0.025.

Habitat.—North Pacific, Station 253, surface.

3. Spongolarcus dimensivus, n. sp.

Spongy network of the shell dense, its meshes four to eight times as broad as the bars. Surface of the shell thorny; diameter of its internal cavity about fifteen times as large as the thickness of its wall. Proportion of the three dimensive axes = 3 : 4 : 5.

Dimensions.—Length 0.2, breadth 0.16, height 0.12; thickness of the spongy wall 0.01.

Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.

4. Spongolarcus amphicentria, Haeckel.

? Amphicentria salpa, Ehrenberg, 1861, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 296; Abhandl. d. k. Akad. d. Wiss. Berlin, 1872, Taf. ii. fig. 18.

? Spongurus salpa, Haeckel, 1862, Monogr. d. Radiol., p. 466.

Spongy network of the shell compact, its meshes about the same breadth as the bars. Surface of the shell spiny, with some larger spines around the poles of the axis; diameter of the internal cavity about six times as large as the thickness of its wall. Proportion of the three dimensive axes = 1 : 2 : 3. (Perhaps this Spongolarcus is identical with Amphicentria salpa, very imperfectly described and figured by Ehrenberg, loc. cit.?)

Dimensions.—Length 0.14, breadth 0.09, height 0.05; thickness of the spongy wall 0.015.

Habitat.—North Atlantic; off Greenland, 1000 fathoms, Ehrenberg; Station 64, depth (2700) fathoms.

Genus 271. Stypolarcus,^[310] n. gen.

Definition.—Larcarida with lentelliptical spongy shell, composed of compact spongy framework, without central cavity and medullary shell (without radial spines).

The genus Stypolarcus differs from Spongolarcus in the absence of any central cavity. This is quite filled up by spongy framework, which forms the whole mass of the lentelliptical body. Stypolarcus bears therefore the same relation to Spongolarcus that Styptosphæra does to Plegmosphæra.

1. Stypolarcus spongiosus, n. sp.

Lentelliptical shell composed in the whole mass of loose, spongy framework of similar texture, with irregular meshes, about ten to twenty times as broad as the thin bars. Surface rough, without radial spines. Proportion of the three axes = 3 : 4 : 5.

Dimensions.—Length 0.2, breadth 0.16, height 0.12.

Habitat.—Antarctic Ocean, Station 157, depth 1950 fathoms.

Family XXV. Larnacida, Haeckel, 1883 (Pl. 50, figs. 3-8).

Definition.—Larcoidea with a regular, completely latticed, lentelliptical cortical shell, without open gates and annular constrictions; either this cortical shell or the enclosed medullary shell is trizonal, composed of three elliptical, latticed, dimensive girdles of different sizes, perpendicular one to another.

The family Larnacida immediately follows the Larcarida as the next simple group of all Larcoidea; some genera of both groups (such as Larnacalpis and Coccolarcus, or Larnacantha and Larcidium) may easily be confounded from their being so much alike. In both the lentelliptical shell is composed of two concentric shells, an inner (medullary) and an outer (cortical) shell. But the connection between these shells and the construction of the inner shell is quite different in the two groups. Whilst in the Larcarida the medullary shell is connected with the cortical shell simply by radial beams, here in the Larnacida this connection is effected by two latticed lamellæ, which are the lateral wings of a transverse girdle. Therefore we encounter here for the first time that peculiar mode of growth which characterises the greater part of the Larcoidea, but particularly the Pylonida. But whilst in the Pylonida between the three crossed lattice-girdles, remain four open gates, here in the Larnacida the gates become closed by lattice-work; the lentelliptical cortical shell becomes perfect.

The most simple genus of Larnacida, and no doubt the common ancestral form of this whole family, is Larnacilla (Pl. 50, figs. 1, 1a, 1b). The most important shell of this typical genus is composed of a simple lentelliptical medullary shell and of three elliptical latticed girdles surrounding it, perpendicular one to another. These three "dimensive girdles" lie in the perimeter of the three dimensive planes, the minor (and first) in the equatorial plane, the second (and major) in the lateral plane, the third (and intermediate) in the sagittal plane. Therefore we have before us the same "trizonal shell" as in the important genus Trizonium among the Pylonida. But whilst in Trizonium, as in all Pylonida, the four gates between the girdles remain open, here in Larnacilla they become perfectly closed by lattice-work.

The formation of the typical "Larnacilla-shell" begins with a simple, spherical or lentelliptical lattice-shell, from both sides of which arise two latticed "lateral wings" opposite on the poles of the transverse axis. These two wings are comparable to the lateral chambers of Tholartus (among the Tholonida), but differ by two large openings. Each wing is a short cylindrical tube with latticed wall, open at both ends; the axis of the tube (going through the centre of the open ends) is parallel to the principal axis of the whole shell (and of the central chamber). Therefore both wings form together a transverse ring, the middle of which encloses the central chamber. The distal parts of both wings grow towards the poles of the principal axis; if they became united here, the second (lateral) girdle would be complete. Between it and the first girdle four open gates remain ("Tetrapyle"); but these become overgrown by the third or sagittal girdle, and at last the gates between this and the two other girdles become closed by lattice-work. This perfect fenestration of the trizonal cortical shell, and the complete closing of the gates between the girdles by network, is the only difference between Trizonium and Larnacilla.

In Larnacilla and in the nearly allied Larnacidium (only differing by radial spines on the surface) the "trizonal shell" is an external or "cortical shell," enclosing the central capsule, the interior of which only contains the simple central chamber and the jointed proximal parts of both lateral wings. In the other genera of Larnacida (by proceeding growth) this trizonal Larnacilla-shell becomes enclosed by the growing central capsule and is now only a "medullary shell," whilst on the outside of the central capsule in the same manner is developed an outer cortical shell (Larnacalpis, Larnacantha); and perhaps the same process may be repeated. But sometimes also this cortical shell becomes doubled by a simple envelop of network (Larnacoma). In the Larnacospongida the cortical shell is composed of a spongy framework (corresponding to the Spongolarcida in the foregoing family).

The lattice-work of the Larnacida is commonly irregular (as in most other Larcoidea), and its pores have little signification for the different species. On the outer surface often arise radial spines, symmetrically disposed either in dimensive planes or in diagonal planes.

The central capsule is constantly a true lentellipsis or a "triaxial ellipsoid," characterised by three halving, elliptical dimensive planes, perpendicular one to another. It bears a different relation to the skeleton in the two subfamilies of Larnacida. In the first subfamily, the Larnacillida (Larnacilla, Larnacidium), the central capsule encloses only the simple spherical or lentelliptical central chamber ("simple medullary shell"), and is enveloped by the trizonal cortical shell. In the other subfamily, the Larnacalpida (Larnacalpis, Larnacospongus, &c.), this trizonal "Larnacilla-shell" becomes enclosed by the overgrowing central capsule, which now becomes enveloped by an external, latticed or spongy, lentelliptical "cortical shell."

Synopsis of the Genera of Larnacida.

II. Subfamily Larnacillida. Medullary shell simple, spherical or subspherical. Cortical shell lentelliptical, trizonal; between them four gates. Shell without radial spines, 272. Larnacilla.

Shell with radial spines, 273. Larnacidium.

II. Subfamily Larnacalpida. Medullary shell Larnacilla-shaped, double; the inner spherical or subspherical, the outer lentelliptical and trizonal. Cortical shell simple or double, but not spongy. Cortical shell simple. Without radial spines, 274. Larnacalpis.

With radial spines, 275. Larnacantha.

Cortical shell double, without radial spines, 276. Larnacoma.

Cortical shell simple or double, wholly or partly spongy. Shell without radial spines, 277. Larnacospongus.

Shell with radial spines, 278. Larnacostupa.

I. Subfamily Larnacillida. Medullary shell simple, spherical or subspherical. Cortical shell lentelliptical, trizonal; between them four gates.

Shell without radial spines,

272. Larnacilla.

Shell with radial spines,

273. Larnacidium.

II. Subfamily Larnacalpida. Medullary shell Larnacilla-shaped, double; the inner spherical or subspherical, the outer lentelliptical and trizonal.

Cortical shell simple or double, but not spongy.

Cortical shell simple.

Without radial spines,

274. Larnacalpis.

With radial spines,

275. Larnacantha.

Cortical shell double, without radial spines,

276. Larnacoma.

Cortical shell simple or double, wholly or partly spongy.

Shell without radial spines,

277. Larnacospongus.

Shell with radial spines,

278. Larnacostupa.

Subfamily 1. Larnacillida, Haeckel.

Definition.—Larnacida with a simple, spherical or lentelliptical, medullary shell, connected by the lateral wings of a latticed transverse girdle with the simple lentelliptical trizonal cortical shell; the central capsule encloses the former and is enveloped by the latter.

Genus 272. Larnacilla,^[311] n. gen.

Definition.—Larnacida with a simple lentelliptical cortical shell, connected by the lateral wings of a latticed transverse girdle with the simple, spherical or lentelliptical, medullary shell. Surface without radial spines.

The genus Larnacilla represents the most simple form of Larnacida, and at the same time the most important common ancestral form, from which the greater number of Larcoidea may be derived, viz., all those genera which possess the characteristic "Larnacilla-shaped medullary shell." This typical form of medullary shell may be derived from the genus Trizonium among the Pylonida by the closing of the four open gates of this genus. The free opening of these four gates becomes overgrown and closed by lattice-work, developed from the free edges of the three crossed girdles, and thus finally all three girdles are united in the form of a simple lentelliptical shell (Pl. 50, figs. 1, 1a, 1b). Seen from the sagittal poles (or from the poles of the shortest axis, fig. 1), the shell exhibits on both sides of the small spherical medullary shell the two lateral wings of the transverse girdle from the face; seen from the lateral poles (or from the poles of the transverse axis, fig. 1a), one of these wings appears in the optical section as an oblong ring, which seemingly encloses the concentric medullary shell, and on both sides is grown together with the sagittal girdle; seen from the principal poles (or from the poles of the longitudinal axis, fig. 1b), both wings exhibit their elliptical opening (at the right and left from the central medullary shell). The two concentric shells are only connected by the two lateral tube-like wings of the transverse girdle; the lateral and the sagittal girdles have no connection with the medullary shell. The latter is sometimes spherical, at other times lentelliptical.

1. Larnacilla typus, n. sp. (Pl. 50, fig. 1, 1a, 1b).

Cortical shell with smooth surface and with subregular network; pores twice as broad as the bars; about twelve pores on the half meridian, ten on the half equator. Proportion of the three dimensive axes = 2 : 3 : 4. Internal four gates (between transverse and lateral girdles) roundish-triangular, little broader than high. Medullary shell spherical, scarcely one-third as broad as the lentelliptical cortical shell.

Dimensions.—Length of the cortical shell (or principal axis) 0.13, breadth of it (or transverse axis) 0.1, height of it (or sagittal axis) 0.07; pores 0.006, bars 0.003; medullary shell (diameter) 0.03.

Habitat.—Pacific, central area, Station 271, depth 2425 fathoms.

2. Larnacilla prometor, n. sp.

Cortical shell with rough surface and regular network; pores three times as broad as the bars; about ten on the half meridian, eight on the half equator. Proportion of the three axes = 1 : 2 : 3. Internal four gates (between transverse and lateral girdles) kidney-shaped, twice as broad as high. Medullary shell lentelliptical, of the same form as the external cortical shell, but only one third as large.

Dimensions.—Length of the cortical shell 0.15, breadth 0.1, height 0.05, pores 0.015, bars 0.005; medullary shell 0.02 to 0.05.

Habitat.—Indian Ocean, Zanzibar, Pullen, depth 2200 fathoms.

3. Larnacilla subglobosa, n. sp.

Cortical shell nearly spherical, with thorny surface and irregular network; pores roundish, twice to four times as broad as the bars; twelve to sixteen in the half circumference. Proportion of the three axes very little different = 1.3 : 1.4 : 1.5. Internal four gates elliptical, one and a half times as broad as high. Medullary shell spherical, one-fourth as broad as the cortical shell.

Dimensions.—Length of the cortical shell 0.15, breadth 0.14, height 0.13; pores 0.006 to 0.012, bars 0.003; medullary shell 0.035.

Habitat.—Pacific, central area. Station 266, depth 2750 fathoms.

4. Larnacilla medullaris, n. sp.

Cortical shell lentelliptical, with smooth surface and irregular network; pores roundish, very small, scarcely as broad as the bars; about eight to nine on the half meridian, six to seven on the half equator. Proportion of the three axes = 3 : 4 : 6. Internal four gates elliptical. Medullary shell spherical, scarcely one-third as broad as the cortical shell. (This small species may be only the medullary shell of some other Larcoid, the cortical shell of which is not yet formed.)

Dimensions.—Length of the cortical shell 0.06, breadth 0.04, height 0.03; pores and bars about 0.004; medullary shell 0.013.

Habitat.—Pacific, central area, Station 265, depth 2900 fathoms.

Genus 273. Larnacidium,^[312] n. gen.

Definition.—Larnacida with a simple lentelliptical cortical shell, connected by the lateral wings of a latticed transverse girdle with the simple, spherical or lentelliptical, medullary shell. Surface armed with radial spines.

The genus Larnacidium has the same shell-formation as the foregoing Larnacilla, and differs from it only in the possession of radial spines on the surface, which in all known species exhibit a symmetrical disposition. From the nearly allied genus Larcidium it differs in the characteristic mode of connection between the two shells, owing to the different kind of growth. In Larcidium this connection is effected only by radial beams, whereas in Larnacidium (as in all Larnacida) by two lateral latticed tubes, the wings of the primary transverse girdle.

1. Larnacidium staurobelonium, n. sp.

Cortical shell smooth, with four strong conical, radial spines in the lateral plane, opposite in pairs, two on the poles of the principal and two on the poles of the transverse axis. Pores subregular, circular, twice as broad as the bars; about twelve on the half meridian. Proportion of the three axes = 2 : 3 : 4. Medullary shell spherical, one-third as broad as the cortical shell.

Dimensions.—Length of the cortical shell 0.12, breadth 0.09, height 0.06; pores 0.008, bars 0.04; medullary shell 0.03.

Habitat.—North Pacific Station 244, depth 2900 fathoms.

2. Larnacidium hexabelonium, n. sp.

Cortical shell thorny, with six strong, three-sided pyramidal, radial spines, lying opposite in pairs on the poles of the three dimensive axes. Pores subregular, circular, three times as broad as the bars; about fourteen on the half meridian. Proportion of the three axes = 2 : 2.5 : 3. Medullary shell spherical, one-third as broad as the cortical shell.

Dimensions.—Length of the cortical shell 0.14, breadth 0.11, height 0.08; pores 0.01, bars 0.003; medullary shell 0.04.

Habitat.—South Pacific, Station 295, depth 1500 fathoms.

3. Larnacidium polybelonium, n. sp.

Cortical shell very spiny, with numerous (twenty to thirty or more) larger thin radial spines, about as long as the shell. Pores irregular, twice to five times as broad as the bars; about sixteen on the half meridian. Proportion of the three axes = 2 : 2.5 : 3. Medullary shell lentelliptical, half as large as the cortical shell.

Dimensions.—Length of the cortical shell 0.11, breadth 0.09, height 0.07; pores 0.004 to 0.01, bars 0.002; length of the medullary shell 0.06, breadth 0.05, height 0.04.

Habitat.—Western Tropical Pacific, Station 225. depth 4475 fathoms.

Subfamily 2. Larnacalpida, Haeckel.

Definition.—Larnacida with a double, trizonal, Larnacilla-shaped medullary shell, enclosed in the central capsule, and enveloped by a simple or double, latticed or spongy, lentelliptical, cortical shell.

Genus 274. Larnacalpis,^[313] n. gen.

Definition.—Larnacida with a simple lentelliptical cortical shell, without radial spines. Medullary shell double, Larnacilla-shaped.

The genus Larnacalpis represents the most simple form of the sub-family Larnacalpida, and is very important as the common original form of all those Larcoidea in which a double Larnacilla-shaped medullary shell is surrounded by a simple, perfectly closed, latticed, lentelliptical cortical shell. Therefore the same typical, trizonal, lentelliptical shell, which in Larnacilla represents the external envelop (or cortical shell) of the central capsule, here in Larnacalpis becomes enclosed as an internal nucleus (or medullary shell) in the interior of the central capsule, and this latter becomes overgrown by a new lentelliptical cortical shell. The connection between the two shells of Larnacalpis is either effected by a number of radial beams (e.g., in Larnacalpis triaxonia by six beams situated in the three dimensive axes), or by two lateral, latticed, tube-like wings, which are repetitions of the smaller lateral wings connecting its external shell with the internal medullary shell (as in Larnacalpis lentellipsis). The latter species may be regarded as a Pylonium with a completely latticed shell.

1. Larnacalpis lentellipsis, n. sp. (Pl. 50, figs. 2, 2a, 2b).

Cortical shell with thorny surface and irregular network; pores roundish, twice to four times as broad as the bars; about sixteen on the half meridian, twelve on the half equator. Proportion of the three dimensive axes = 2 : 3 : 4. Medullary shell one-third as large as the cortical, with four elliptical internal gates, connected with it by two opposite beams in the principal axis and by two latticed wings in the transverse axis; therefore between the two shells are four large kidney-shaped gates, halved by the polar beams (as in Octopyle).

Dimensions.—Length of the cortical shell (or principal axis) 0.14, breadth (or transverse axis) 0.11, height (or sagittal axis) 0.07; pores 0.01 to 0.02, bars 0.005; length of the medullary shell 0.05, breadth 0.04, height 0.03.

Habitat.—Pacific, central area, Station 273, depth 2600 fathoms.

2. Larnacalpis phacodiscus, n. sp.

Cortical shell with thorny surface and regular network; pores circular, twice as broad as the bars; about ten on the half meridian, eight on the half equator. Proportion of the three axes = 2 : 2.5 : 3. Medullary shell half as large as the cortical, with four kidney-shaped internal gates.

Dimensions.—Length of the cortical shell 0.13, breadth 0.11, height 0.09; pores 0.012, bars 0.006; length of the medullary shell 0.06, breadth 0.045, height 0.03.

Habitat.—North Pacific, Station 253, depth 3125 fathoms.

3. Larnacalpis macrococcus, n. sp.

Cortical shell with spiny surface and regular network; pores circular, small, of the same breadth as the bars; about twenty-two on the half meridian, nineteen on the half equator. Proportion of the three axes = 2 : 3 : 4. Medullary shell two-thirds as large as the cortical, with four wide internal semicircular gates.

Dimensions.—Length of the cortical shell 0.1, breadth 0.075, height 0.05; pores and bars 0.003; length of the medullary shell 0.066, breadth 0.05, height 0.032.

Habitat.—Western Tropical Pacific, Station 224, depth 1850 fathoms.

4. Larnacalpis subsphærica, n. sp.

Cortical shell with rough surface and irregular network; roundish pores twice to five times as broad as the bars; about twenty-four on the half meridian, twenty-one on the half equator. Proportion of the three axes = 1.2 : 1.3 : 1.4. Medullary shell half as large as the cortical, with four elliptical internal gates.

Dimensions.—Length of the cortical shell 0.14, breadth 0.13, height 0.12; pores 0.004 to 0.01, bars 0.002; length of the medullary shell 0.08, breadth 0.07, height 0.06.

Habitat.—Pacific, central area, Station 266, depth 2750 fathoms.

5. Larnacalpis triaxonia, n. sp. (Pl. 50, fig. 3).

Cortical shell with smooth surface and peculiar network, composed of four meridian rows of larger pores (five large elliptical pores on each half meridian, the largest in the equator) and numerous small irregular pores between them. Proportion of the three axes = 2 : 3 : 4. Medullary shell with four semicircular internal gates, about one-fourth as large as the cortical, connected with it by six thin radial beams, opposite in pairs in the three dimensive axes.

Dimensions.—Length of the cortical shell 0.14, breadth 0.1, height 0.07; large pores 0.03, small pores 0.002 to 0.01, bars 0.002 to 0.01; length of the medullary shell 0.04, breadth 0.03, height 0.02.

Habitat.—Pacific, central area, Station 263, depth 2650 fathoms.

Genus 275. Larnacantha,^[314] n. gen.

Definition.—Larnacida with a simple lentelliptical cortical shell, armed with symmetrically disposed radial spines. Medullary shell double, Larnacilla-shaped.

The genus Larnacantha has the same characteristic shell-formation as the foregoing Larnacalpis, and differs from it only in the possession of radial spines, which are symmetrically distributed on the surface in a definite order. Commonly these spines are external prolongations of the internal radial beams, which connect the double Larnacilla-shaped medullary shell with the simple lentelliptical cortical shell.

1. Larnacantha dissacantha, n. sp.

Cortical shell smooth, with two large cylindrical spines, opposite on the poles of the principal axis, and somewhat longer than it. Pores regular, circular, three times as broad as the bars; about eleven on the half meridian. Proportion of the three axes = 2 : 3 : 4. Medullary shell one-third as large as the cortical shell.

Dimensions.—Length of the cortical shell (principal axis) 0.13, breadth (transverse axis) 0.1, height (sagittal axis) 0.07; pores 0.009, bars 0.003; length of the Larnacilla-shaped medullary shell 0.045.

Habitat.—North Pacific, Station 256, depth 2950 fathoms.

2. Larnacantha stauracantha, n. sp.

Cortical shell smooth, with four large conical spines in the lateral plane, two larger opposite on the poles of the principal, two smaller on those of the transverse axis. Pores regular, circular, twice as broad as the bars; about seventeen on the half meridian. Proportion of the three axes = 3 : 3.5 : 4. Medullary shell one-third as large as the cortical shell.

Dimensions.—Length of the cortical shell 0.15, breadth 0.13, height 0.11; pores 0.008, bars 0.004; length of the medullary shell 0.05.

Habitat.—Pacific, central area, Station 274, surface.

3. Larnacantha quadricornis, n. sp.

Cortical shell spiny, with four strong, horn-like curved spines in the lateral plane, opposite in pairs on the poles of the crossed diagonal axes. Pores irregular, roundish, twice to four times as broad as the bars; about fourteen on the half meridian. Proportion of the three axes = 2 : 3 : 4. Medullary shell one-third as large as the cortical shell.

Dimensions.—Length of the cortical shell 0.14, breadth 0.11, height 0.07; pores 0.006 to 0.012, bars 0.003; length of the medullary shell 0.05.

Habitat.—Pacific, central area, Station 270, surface.

4. Larnacantha hexacantha, n. sp. (Pl. 50, fig. 4).

Cortical shell thorny, with six strong conical radial spines in the lateral plane, two opposite on the poles of the principal axis, four others opposite in pairs on the poles of the two crossed diagonal axes. Pores with peculiar distribution; twelve large elliptical pores (nearly of the size of the medullary shell) symmetrically disposed in four crossed meridians (between the sagittal and the lateral meridians), separated by bands of smaller irregular pores. Proportion of the three axes = 3 : 4 : 5. Medullary shell hexagonal, one-third as large as the cortical shell.

Dimensions.—Length of the cortical shell 0.14, breadth 0.11, height 0.08; large pores 0.04, small pores 0.003 to 0.01, bars 0.004; length of the medullary shell 0.05.

Habitat.—Pacific, central area, Station 263, depth 2650 fathoms.

5. Larnacantha bicruciata, n. sp. (Pl. 50, fig. 5).

Cortical shell thorny, in the lateral plane with eight strong conical radial spines, alternating with eight smaller spines; four of the eight stronger spines opposite on the poles of the principal and transverse axes (in the figure 5, by mistake, not represented large enough), four others between those, opposite on the poles of the two crossed diagonal axes. Pores with a peculiar disposition; on both flat sides of the lentellipsis an elliptical ring of eight large elliptical pores (alternating with the eight stronger radial spines), separated by bands of smaller irregular pores. Proportion of the three axes = 2 : 3 : 4. Medullary shell nearly half as long as the cortical shell.

Dimensions.—Length of the cortical shell 0.16, breadth 0.13, height 0.08; large pores 0.03, small pores 0.003 to 0.01, bars 0.006; length of the medullary shell 0.07.

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

6. Larnacantha octacantha, n. sp.

Cortical shell thorny, with eight long and thin, cylindrical, radial spines, lying opposite in pairs in two crossed diagonal planes. Pores irregular, roundish, twice to five times as broad as the bars; about sixteen on the half meridian. Proportion of the three axes = 1 : 1⅓ : 2. Medullary shell scarcely one-fourth as long as the cortical shell. (This species resembles closely the common Tetrapyle octacantha, from which it seems to be developed by a complete over-growing of the four gates, which become closed by a network connecting the free edges of the transverse and lateral girdles.)

Dimensions.—Length of the cortical shell 0.18, breadth 0.13, height 0.1; pores 0.005 to 0.015, bars 0.003; length of the medullary shell 0.04.

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

7. Larnacantha cladacantha, n. sp.

Cortical shell very spiny, with eight longer ramified spines, lying opposite in pairs in two crossed diagonal planes; each spine with two to six irregular, lateral branches. Pores irregular, roundish, twice to three times as broad as the bars; about twelve on the half meridian. Proportion of the three axes = 5 : 6 : 7. Medullary shell nearly half as long as the cortical shell. (Differs from the foregoing by the branching spines end the larger medullary shell.)

Dimensions.—Length of the cortical shell 0.15, breadth 0.13, height 0.11; pores 0.01 to 0.015, bars 0.005; length of the medullary shell 0.07.

Habitat.—Indian Ocean, surface, Cocos Islands (Rabbe).

8. Larnacantha prismatica, n. sp. (Pl. 50, fig. 6).

Cortical shell smooth, four-sided prismatic, with eight short, parallel, three-sided pyramidal spines; these lie opposite in pairs in four parallel longitudinal lines, as prolongations of the four lateral edges of the prism, and arise from its eight corners. Pores regular, circular, three times as broad as the bars; about fourteen on the half meridian. Proportion of the three axes = 2 : 3 : 4. Medullary shell half as long as the cortical shell.

Dimensions.—Length of the cortical shell 0.11, breadth 0.07, height 0.05; pores 0.006, bars 0.002; length of the medullary shell 0.06.

Habitat.—Pacific, central area, Station 263, depth 2650 fathoms.

9. Larnacantha decacantha, n. sp.

Cortical shell thorny, with ten short and stout, conical, radial spines, two opposite on the poles of the principal axis (as prolongations of inner axial beams), eight others opposite in pairs in two crossed diagonal planes. Pores irregular, roundish, twice to four times as broad as the bars; about sixteen on the half meridian. Proportion of the three axes = 3 : 3.75 : 4. Medullary shell about one-third as long as the cortical shell.

Dimensions.—Length of the cortical shell 0.16, breadth 0.15, height 0.12; pores 0.008 to 0.016, bars 0.004; length of the medullary shell 0.06.

Habitat.—North Atlantic, Station 354, surface.

10. Larnacantha dodecantha, n. sp.

Cortical shell nearly smooth, but with twelve strong conical radial spines; four in the lateral plane opposite in pairs (two on the poles of the principal, and two on the poles of the transverse axis); eight others opposite in pairs in two crossed diagonal planes. Pores with a peculiar disposition: twelve large elliptical pores in two crossed meridian planes (alternating with the twelve spines), separated by bands of irregular small pores. Proportion of the three axes = 1 : 1.5 : 2. Medullary shell hexagonal, one-third as long as the cortical shell.

Dimensions.—Length of the cortical shell 0.15, breadth 0.11, height 0.08; large pores 0.03, small pores 0.005 to 0.01, bars 0.003; length of the medullary shell 0.05.

Habitat.—Pacific, central area, Station 265, depth 2900 fathoms.

11. Larnacantha drymacantha, n. sp.

Cortical shell very spiny, on the whole surface covered with a forest of numerous (thirty to fifty or more) large branched spines, about the length of the shell; each spine with three to nine lateral branches, simple or forked (very similar to Cromyodrymus abietinus, Pl. 30, fig. 6). Pores very irregular, roundish. Proportion of the three axes = 2 : 2.5 : 3. Medullary shell half as long as the cortical shell.

Dimensions.—Length of the cortical shell 0.16, breadth 0.13, height 0.1; pores 0.005 to 0.015, bars 0.03; length of the medullary shell 0.08.

Habitat.—Pacific, central area, Station 271, depth 2425 fathoms.

Genus 276. Larnacoma,^[315] n. gen.

Definition.—Larnacida with double lentelliptical cortical shell, without radial spines. Medullary shell double, Larnacilla-shaped.

The genus Larnacoma has originated from the nearly allied Larnacalpis by duplication of the cortical shell. Whilst in both genera the connection between the Larnacilla-shaped medullary shell and the primary cortical shell is the same, many short radial beams arise from the surface of the latter in Larnacoma, which at constant equal distances from it unite by a network forming the secondary or outer cortical shell. It differs from the similar Druppulida (Cromyodruppa) by the sagittal flattening of the lentelliptical shell and the Larnacilla-form of the double medullary shell.

1. Larnacoma lentellipticum, n. sp.

Shell with smooth surface and elliptical perimeter, one and a third times as long as broad. All four shells lentelliptical. Distance between the two cortical shells about twice as great as the distance of the inner cortical and outer medullary shell. Network of both outer shells irregular, with large roundish pores, twice to six times as broad as the bars.

Dimensions.—Length (or principal axis) of the first (innermost) shell 0.03, second 0.08, third 0.16, fourth (outermost) 0.27, breadth (or transverse axis) corresponding—(A) 0.02, (B) 0.05, (C) 0.11, (D) 0.2.

Habitat.—South Atlantic, Station 323, depth 1900 fathoms.

2. Larnacoma quadruplex, n. sp.

Shell with thorny surface and elliptical perimeter, one and a fifth times as long as broad. All four shells lentelliptical. Distance between the two cortical shells somewhat smaller than the distance between the inner cortical and outer medullary shell. Network of both outer shells irregular, with large roundish pores, twice to ten times as broad as the bars.

Dimensions.—Length of the first shell 0.02, second 0.06, third 0.15, fourth 0.24; breadth corresponding—(A) 0.016, (B) 0.04, (C) 0.11, (D) 0.2.

Habitat.—South Atlantic, Station 335, depth 1425 fathoms.

3. Larnacoma hexagonium, n. sp.

Shell with thorny surface and hexagonal perimeter, as long as broad. All four shells hexagonal, connected by six piercing radial beams (two in the principal axis, four others in two crossed diagonals). Distance between the two cortical shells somewhat greater than the distance between the inner cortical and outer medullary shell. Network of both outer shells subregular, with small circular pores, twice as broad as the bars.

Dimensions.—Length of the first shell 0.02, second 0.05, third 0.09, fourth 0.16; breadth corresponding—(A) 0.015, (B) 0.035, (C) 0.065, (D) 0.12.

Habitat.—South Atlantic, west of Tristan da Cunha, Station 332, depth 2200 fathoms.

Genus 277. Larnacospongus,^[316] n. gen.

Definition.—Larnacida with spongy lentelliptical cortical shell, without radial spines. Medullary shell double, Larnacilla-shaped.

The genus Larnacospongus differs from the nearly allied genera Larnacalpis and Larnacoma by the spongy texture of the lentelliptical cortical shell whilst the enclosed medullary shell in both genera is the same trizonal Larnacilla-shell. Therefore Larnacospongus (and the following nearly related Larnacostupa) can be derived directly by development of a spongy envelop either from Larnacilla and Larnacalpis, or from Trizonium and Amphipyle. But some species of these spongy genera appear to be derived rather from Tetrapyle or Pylonium, perhaps also from Cubotholus. Their phylogenetic origin may be explained in different ways.

1. Larnacospongus larnacillifer, n. sp.

Cortical shell lentelliptical, one and a half times as long as broad, with rough surface and rather loose spongy framework, directly enclosing a trizonal Larnacilla-shell of the same form, but of only one-third its size.

Dimensions.—Length of the whole shell 0.17, breadth 0.12; length of the medullary shell 0.06, breadth 0.04.

Habitat.—South Atlantic, east coast of Patagonia, Station 319, surface.

2. Larnacospongus tetrapylifer, n. sp.

Cortical shell lentelliptical, one and a third times as long as broad, with thorny surface; composed of an outer envelop of loose spongy framework and an inner lattice-shell with four kidney-shaped gates, like Tetrapyle; the latter encloses a trizonal medullary shell of one-fourth its size.

Dimensions.—Length of the whole shell 0.22, breadth 0.16; length of the medullary shell 0.045, breadth 0.035.

Habitat.—South Atlantic, west of Tristan da Cunha, Station 332, surface.

Genus 278. Larnacostupa,^[317] n. gen.

Definition.—Larnacida with spongy lentelliptical cortical shell, with radial spines on the surface. Medullary shell double, Larnacilla-shaped.

The genus Larnacostupa differs from the preceding Larnacospongus only in the possession of radial spines, covering either the whole surface irregularly or disposed in a certain symmetrical order.

1. Larnacostupa octacantha, n. sp.

Cortical shell lentelliptical, with thorny surface, and rather dense, irregular, spongy framework, which arises from an inner latticed cortical shell, like that of Tetrapyle or Pylonium. This latter is twice as large as the enclosed Larnacilla-shell. Eight long and thin, cylindrical, radial spines, opposite in pairs in two diagonal planes. (Seems to be the common Tetrapyle octacantha, enveloped by an outer spongy framework mantle.)

Dimensions.—Length of the whole shell (without spines) 0.22, breadth 0.16; length of the medullary shell 0.06, breadth 0.04.

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

2. Larnacostupa spinosa, n. sp.

Cortical shell lentelliptical, about one and a half times as long as broad, with very lax and irregular spongy framework, arising from a nearly quadrangular lattice-shell like that of Tetrapyle; this latter encloses a Larnacilla-shell of half its size. Whole surface covered with thin bristle-like radial spines, of about the length of the shell.

Dimensions.—Length of the whole shell (without spines) 0.18, breadth 0.12; length of the medullary shell 0.05, breadth 0.035.

Habitat.—Antarctic Ocean, off Kerguelen, Station 150, surface.

3. Larnacostupa dendrophora, n. sp.

Cortical shell nearly spherical, scarcely longer than broad, with lax, irregular spongy framework, arising from a lentelliptical trizonal medullary shell (like Larnacilla). Whole surface covered with thin arborescent radial spines, about half as long as the shell, each spine with three to six irregular branches.

Dimensions.—Length of the whole shell (without spines) 0.15, breadth 0.13; length of the medullary shell 0.07, breadth 0.04.

Habitat.—Antarctic Ocean, Station 154, surface.

Family XXVI. Pylonida, Haeckel, 1881 (Pl. 9).

Pylonida, Haeckel, 1881, Prodromus, p. 463.

Definition.—Larcoidea with regular, incompletely latticed cortical shell, distinguished by two to four or more symmetrically disposed gates or large fissures remaining between one to three latticed dimensive girdles (perpendicular one to another). One, two, or three concentric systems of such girdles (each system with three girdles) may be developed.

The family Pylonida is the most important and interesting among all the Larcoidea, not only because it is much richer in different and peculiar forms than the other families of this section, but also because it has direct and very complex relations to all the other families of Larcoidea. It is even possible that the Pylonida represent the original ancestral group of the whole section, and that the apparently simpler group of the Larcarida must be derived from the former by retrogressive metamorphosis.

Till the year 1881 the family Pylonida, which here now exhibits ten genera with eighty-six species, was only represented by one single species, accurately described and extensively illustrated by Johannes Müller in 1858, the well known and widely distributed cosmopolitan Tetrapyle octacantha (Abhandl. d. k. Akad. d. Wiss. Berlin, p. 33, Taf. iii.). A slight modification of it was afterwards described by Ehrenberg as Schizomma quadrilobum (Abhandl. d. k. Akad. d. Wiss. Berlin, 1872, Taf. ii. fig. 12). A more accurate description of it, with a good explanation of its characteristic growth, was given in 1879 by Richard Hertwig in his Organismus der Radiolarien (pp. 52-54, Taf. iv. figs. 7, 8; Taf. vi. figs. 2, 5). In my Prodromus (1881, p. 463) I constituted for a large number of allied species, detected in the Challenger collection, the special family Pylonida, and distinguished among it twelve different genera. However, I think it now better to restrict the definition of the family as given in the above definition, and to remove from it a number of genera formerly with it united, as the genera Triopyle and Hexapyle, appertaining to the Discoidea.

The characteristic type of all true Pylonida is clearly demonstrated by their peculiar mode of growth, the consequence of which is the imperfect lattice-work of the fenestrated larcoid shell. This remarkable growth is effected by the development of elliptical latticed girdles (or rings), which enclose a quite simple, spherical, subspherical, or lentelliptical primordial shell. The girdles lie in three different planes, perpendicular to one another, and are of different sizes; each girdle being somewhat larger than the foregoing and somewhat smaller than the following girdle. Between these latticed girdles remain on the surface of the shell large openings or "gates," which are not closed by network, and it is just the symmetrical disposition and form of these open "gates," separated and enclosed by the fenestrated girdles, which give to the Pylonida their characteristic appearance.

To understand clearly this peculiar constitution of the Pylonida-shell by a system of alternating girdles, developing one after the other it is indispensable to pay careful attention to the three different elliptical dimensive planes, which characterise all Larcoidea, and to the three different dimensive axes, which bisect those planes. The girdle which first develops around simple primordial shell or central chamber is the transverse girdle, lying in the equatorial plane; then comes, secondly, the lateral girdle, lying in the lateral plane; and thirdly follows the sagittal girdle, lying in the sagittal or median plane. The three simplest genera of the Pylonida—Monozonium, Dizonium, Trizonium—represent these three different stages, with one, two, or three girdles. These three genera constitute the first subfamily, Haplozonaria (with one single system of girdles); all three girdles lie in the surface of a simple lentelliptical cortical shell.

From this first subfamily the other two subfamilies of Pylonida must be derived, by repetition of the same characteristic process of growth. In the Diplozonaria a second system of girdles has been developed, constituting a second (outer) cortical shell of lentelliptical form, concentric with the first. Also in this second system the transverse girdle is first developed, secondly the lateral girdle, thirdly the sagittal girdle. The three genera Amphipyle, Tetrapyle (with Octopyle), and Pylonium represent these three different stages of growth.

Commonly the growth of the Pylonida stops with the completion of the second system but sometimes the same process is once repeated and a third system of girdles is formed, constituting a third lentelliptical shell; in this case also the succession of the three latticed girdles is the same; firstly the (third) transverse girdle is formed, secondly the (third) lateral girdle, and thirdly the (third) sagittal girdle. Each of these three girdles of the third system encloses concentrically the corresponding girdles of the second and first system. The three corresponding genera of this third subfamily (Triplozonaria) are Amphipylonium, Tetrapylonium, and Pylozonium. But in general this highest number of girdles (nine) is very seldom reached; commonly the growth of the Pylonida stops with five girdles (Tetrapyle and Octopyle). More than nine girdles I have never observed, though there remains the possibility of the apposition of a fourth system owing to the peculiar imperfect character of the growth itself.