Legion I. SPUMELLARIA, (continued 17)

Subgenus 1. Tholomantha, Haeckel.

Definition.—Surface of the shell smooth, without radial spines.

1. Tholoma quadrigeminum, n. sp. (Pl. 10, fig. 10).

All four chambers in each cortical shell nearly equal, subregular. Surface smooth, without radial spines. Structure of the network in both shells similar. Pores regular, circular, twice as broad as the bars; six to eight in the basal semicircle of one inner, ten to twelve in the semicircle of one outer cupola.

Dimensions.—Diameter of the outer shell 0.14, of the inner 0.09; pores 0.006, bars 0.003.

Habitat.—South Pacific, Station 302, surface.

Subgenus 2. Tholomura, Haeckel.

Definition.—Surface of the shell with radial spines.

2. Tholoma metallasson,^[334] n. sp. (Pl. 10, fig. 13).

Two opposite chambers in each cortical shell larger than the two others; the larger chambers of the inner shell corresponding to the smaller chambers of the outer shell. Network in both shells of the same structure, regular, with circular, hexagonally framed pores of the same breadth as the bars; eight to ten in the semicircle of an inner, fourteen to sixteen in the semicircle of an outer cupola. Numerous (twenty to thirty or more) thin, cylindrical, bristle-shaped, long radial spines, symmetrically disposed.

Dimensions.—Major axis of the outer shell 0.26, minor axis 0.2; major axis of the inner shell 0.16, minor axis 0.13; pores and bars 0.006.

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

Genus 295. Staurotholus,^[335] n. gen.

Definition.—Tholonida with simple cortical shell (without external veil), composed of four hemispherical cupolas in cross-form, opposite in pairs on the poles of two axes perpendicular one to another; central chamber Larnacilla-shaped (with enclosed medullary shell).

The genus Staurotholus differs from Tholostaurus in the possession of a medullary shell in the central chamber, and may be derived from this genus by its production. But it may also be derived from Amphitholus by apposition of two secondary opposite cupolas between the two primary cupolas. The symmetrical position of an increasing number of radial spines in the different species is remarkable (resembling Tholostaurus as well as Amphitholus).

Subgenus 1. Staurotholissa, Haeckel.

Definition.—Surface of the shell smooth or rough, without radial spines.

1. Staurotholus quadratus, n. sp.

Surface of the cortical shell smooth. All four cupolas nearly of the same size and form; therefore principal and lateral axes equal. Pores regular, circular, with hexagonal frames, twice as broad as the bars; eight to ten on the basal semicircle of one cupola. Medullary shell square.

Dimensions.—Diameter of the cortical shell 0.15; pores 0.01, bars 0.005.

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

2. Staurotholus cruciatus, n. sp.

Surface of the cortical shell rough. The two principal cupolas somewhat larger than the two lateral cupolas; therefore the longitudinal axis longer than the transverse. Pores irregular, roundish, twice to three times as broad as the bars; twelve to sixteen in the semicircle of one cupola.

Dimensions.—Major axis of the shell 0.16, minor 0.13; pores 0.005 to 0.009, bars 0.003.

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

Subgenus 2. Staurotholura, Haeckel.

Definition.—Surface of the shell with radial spines.

3. Staurotholus tetrastylus, n. sp. (Pl. 10, fig. 8).

The two principal cupolas smaller than the two lateral cupolas. Pores subregular, circular, three times as broad as the bars; six to eight in the semicircle of one cupola. Medullary shell elliptical. On the surface four long cylindrical radial spines; two in the principal and two in the lateral axis.

Dimensions.—Major axis of the cortical shell 0.15, minor 0.12; pores 0.012, bars 0.004.

Habitat.—South Pacific, Station 166, surface.

4. Staurotholus octostylus, n. sp.

The two lateral cupolas larger than the two principal cupolas. Pores subregular, circular, twice as broad as the bars; ten to twelve in the semicircle of one cupola. Medullary shell hexagonal, connected with each ring-like constriction by eight strong cylindrical radial spines (longer than the whole shell), lying in two crossed meridian planes, and corresponding to the eight diagonal wing-spines of Tetrapyle octacantha.

Dimensions.—Major axis of the cortical shell 0.12, minor 0.1; pores 0.008, bars 0.004.

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

5. Staurotholus decastylus, n. sp.

The two principal cupolas twice as broad and high as the two lateral cupolas. Pores subregular, circular, four times as broad as the bars; six to eight in the semicircle of one cupola. Ten long and thin radial spines with thickened conical bases, about as long as the major axis of the shell, by inner prolongations connected with the lentelliptical medullary shell; two polar spines in the principal axis, eight wing-spines in two crossed diagonal planes.

Dimensions.—Major axis 0.12, minor 0.1; pores 0.012, bars 0.003.

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

6. Staurotholus dodecastylus, n. sp. (Pl. 10, fig. 9).

The two lateral cupolas larger than the two principal cupolas. Pores subregular, circular, three times as broad as the bars; five to seven in the semicircle of one cupola. Twelve strong cylindrical radial spines, four on the poles of the two larger axes (two principal and two lateral), eight wing-spines in two crossed diagonal planes. Medullary shell hexagonal.

Dimensions.—Major (lateral) axis 0.11, minor (principal) 0.09; pores 0.009, bars 0.003.

Habitat.—Tropical Atlantic, Station 348, surface.

7. Staurotholus polystylus, n. sp.

The two principal cupolas larger than the two lateral cupolas. Pores irregular, roundish, twice to three times as broad as the bars; ten to twelve in the semicircle of one cupola. On the surface numerous thin bristle-shaped spines (twenty to thirty or more).

Dimensions.—Major axis 0.14, minor 0.11; pores 0.006 to 0.01, bars 0.003.

Habitat.—North Pacific, Station 231, surface.

Genus 296. Staurotholonium,^[336] n. gen.

Definition.—Tholonida with double cortical shell (with external veil), composed of four hemispherical cupolas in cross-form, opposite in pairs on the poles of two axes perpendicular one to another; central chamber Larnacilla-shaped (with medullary shell).

The genus Staurotholonium differs from the nearly allied Staurotholus (its probable ancestral form) only in the duplication of the cortical shell. The outer shell commonly repeats the cross-form of the inner, with four corresponding cupolas; but sometimes the four cupolas of the outer shell alternate in size and form with those of the inner, or the outer shell forms a simple lenticular envelope around the inner. From the similar Tholoma, Staurotholonium differs in the possession of a medullary shell in the central chamber.

Subgenus 1. Staurotholodes, Haeckel.

Definition.—Surface of the outer cortical shell smooth or rough, without radial spines.

1. Staurotholonium biquadratum, n. sp.

Outer cortical shell smooth, of the same regular crucial form as the inner, equidistant from it everywhere. Form and structure of both cortical shells nearly the same, but the outer about twice as large as the inner; both connected only by eight diagonal beams. All four cupolas of each cortical shell regular, of the same size. Pores regular, circular, twice as broad as the bars; six to eight in the basal semicircle of each cupola. Medullary shell square. (Similar to Staurotholus quadratus, but differs by the double cortical shell.)

Dimensions.—Diameter of the outer cortical shell 0.16, of the inner 0.08, of the medullary shell 0.04; pores of the inner cortical shell 0.006, bars 0.003.

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

2. Staurotholonium bicruciatum, n. sp.

Outer cortical shell rough, twice as large as the inner, of the same form and structure, at an equal distance from it. In both shells the principal cupolas are larger than the lateral. Pores irregular, roundish, in the outer shell four times, in the inner twice as large as the bars; eight to ten in the basal semicircle of one cupola. (Similar to Staurotholus cruciatus, but differs mainly in the double cortical shell.) Medullary shell lentelliptical.

Dimensions.—Major (longitudinal) axis of the outer cortical shell 0.016, of the inner 0.08; minor (transverse) axis of the former 0.14, of the latter 0.07; medullary shell 0.03 to 0.04.

Habitat.—Pacific, central area, Station 267, depth 2700 fathoms.

3. Staurotholonium alternatum, n. sp.

Outer cortical shell smooth, very different from the inner; in the outer the two principal cupolas are larger than the two lateral; in the inner inversely smaller. Pores subregular, circular, in the outer shell four times, in the inner shell twice as broad as the bars; ten to twelve pores in the basal semicircle of one cupola.

Dimensions.—Major axis (length) of the outer cortical shell 0.15, minor (breadth) 0.13; pores 0.012, bars 0.003; major axis (length) of the inner cortical shell 0.11, minor axis (breadth) 0.09; pores 0.006, bars 0.003.

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

4. Staurotholonium lenticulare, n. sp.

Outer cortical shell smooth, lenticular, with circular circumference, with very delicate irregular network and small roundish pores. Its distance from the inner much greater in the four diagonal points than in the four polar points. Inner cortical shell regular, cross-like, with four cupolas of similar size and form. Pores subregular, circular, twice as broad as the bars; eight to ten in the basal semicircle of one cupola. Medullary shell lenticular.

Dimensions.—Diameter of the outer cortical shell 0.16, of the inner 0.12; pores of the inner 0.008, bars 0.004.

Habitat.—North Atlantic, Station 353, surface.

Subgenus 2. Staurotholoma, Haeckel.

Definition.—Surface of the outer cortical shell with radial spines or thorns.

5. Staurotholonium octodoratium, n. sp.

Outer cortical shell of the same form and structure as the inner, but twice as large, both principal domes somewhat larger than both lateral. Pores subregular, circular, of the same breadth as the bars; five to six in the semicircle of one inner, eight to ten of one outer cupola. Eight thin and long bristle-like spines, opposite in pairs in two crossed diagonal planes.

Dimensions.—Major axis of the outer cortical shell 0.15, minor 0.12; major axis of the inner cortical shell 0.07, minor 0.06; pores and bars 0.005.

Habitat.—North Pacific, Station 231, surface.

6. Staurotholonium octodoronium, n. sp. (Pl. 10, fig. 11).

Outer cortical shell of the same form as the inner, both little distant; network of the outer irregular and delicate. Pores of the inner regular, circular, twice as broad as the bars; seven to nine in the basal semicircle of one cupola. Both lateral domes larger than the principal. Eight long and thin, cylindrical radial spines opposite in pairs in two crossed diagonal planes.

Dimensions.—Major axis of the outer cortical shell 0.2, minor 0.18; major axis of the inner cortical shell 0.16, minor 0.14; pores 0.008, bars 0.004.

Habitat.—South Pacific, Station 288, surface.

Subfamily 3. Cubotholida, Haeckel.

Definition.—Tholonida with triaxial growth; cupolas lying in pairs on the six sides of a cubical central chamber, opposite at the poles of three axes perpendicular one to another. (Shell commonly seven-chambered, with six domes surrounding the central chamber.)

Genus 297. Tholocubus,^[337] n. gen.

Definition.—Tholonida with simple cortical shell (without external veil), composed of six hemispherical cupolas, opposite in pairs on the poles of three axes perpendicular one to another, covering six sides of the simple cuboidal central chamber (without medullary shell).

The genus Tholocubus is the most simple form of the Cubotholida, or of the Tholonida with domes situated in three axes perpendicular one to another; six hemispherical cupolas lying on the six sides of a cuboidal central chamber; this latter contains no medullary shell. Tholocubus may be derived phylogenetically either from Tholostaurus by apposition of two opposite domes on the flat sides of the cross-shell, or from Cubotholus by loss of the medullary shell.

Subgenus 1. Tholocubulus, Haeckel.

Definition.—Surface of the shell smooth or rough, without radial spines.

1. Tholocubus tessellatus, n. sp. (Pl. 10, fig. 12).

Surface of the shell smooth, without radial spines. Pores regular, circular, hexagonally framed, twice as broad as the bars; eight to twelve pores on the semicircle of one cupola. Principal cupolas smaller than the lateral, larger than the sagittal cupolas.

Dimensions.—Diameter of the shell 0.15; pores 0.01, bars 0.005.

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

2. Tholocubus tesserarius, n. sp.

Surface of the shell rough, without radial spines. Pores irregular, roundish, once to three times as broad as the bars; twelve to sixteen pores in the semicircle of one cupola. All six cupolas nearly of the same size.

Dimensions.—Diameter of the shell 0.16; pores 0.004 to 0.008, bars 0.003.

Habitat.—North Atlantic, Station 353, depth 2965 fathoms.

Subgenus 2. Tholocubitus, Haeckel.

Definition.—Surface of the shell with radial spines or thorns.

3. Tholocubus tesseralis, n. sp. (Pl. 10, fig. 16).

Surface of the shell with numerous (eight to sixteen) thin and long, bristle-shaped radial spines (the greater part broken off in the figured specimen); pores subregular, circular, three to four times as broad as the bars; ten to twelve in the semicircle of one cupola.

Dimensions.—Major axis of the shell 0.16, minor axis 0.14; pores 0.01, bars 0.0027.

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

Genus 298. Tholonium,^[338] n. gen.

Definition.—Tholonida with double cortical shell (with external veil), composed of six hemispherical cupolas, opposite in pairs on the poles of three axes perpendicular one to another, covering six sides of the simple cuboidal central chamber (without medullary shell).

The genus Tholonium (Pl. 10, fig. 17) differs from the preceding Tholocubus only in the duplication of the cortical shell. The outer (secondary) shell forms either a simple (spheroidal or ellipsoidal) thin veil around the inner (primary) shell, or both shells are of the same form, with six corresponding cupolas. Possibly Tholonium is the offspring of Cubotholonium, having originated by loss of the medullary shell.

Subgenus 1. Tholonetta, Haeckel.

Definition.—Surface of the shell smooth or rough, without radial spines or thorns.

1. Tholonium bicubicum, n. sp.

Outer shell with six hemispherical dome-shaped protuberances, corresponding in those of the inner shell. Both shells connected by numerous radial beams. Surface of the outer shell smooth; its network nearly of the same shape as that of the inner, with subregular, circular pores, twice as broad as the bars; ten to fifteen pores on the semicircle of one cupola.

Dimensions.—Diameter of the outer shell 0.14, of the inner 0.12; pores of the latter 0.006, bars 0.003.

Habitat.—South Atlantic, Station 325, depth 2650 fathoms.

2. Tholonium ellipticum, n. sp.

Outer shell ellipsoidal, without dome-shaped protuberances, with smooth surface, without radial spines; network delicate, with subregular, circular pores. Inner shell with regular, circular, hexagonally framed pores, twice as broad as the bars; ten to twelve pores on the semicircle of one cupola.

Dimensions.—Major axis of the outer shell 0.16, minor axis 0.14; major axis of the inner shell 0.14, minor axis 0.12; pores 0.008, bars 0.004.

Habitat.—Pacific central area, Station 267, depth 2700 fathoms.

3. Tholonium sphæricum, n. sp.

Outer shell spherical, without dome-shaped protuberances, with smooth surface, without radial spines; network very delicate, with very small subregular, circular pores. Inner shell with regular, circular pores of the same breadth as the bars; fourteen to sixteen on the basal semicircle of one cupola.

Dimensions.—Diameter of the spherical outer shell 0.15, inner shell 0.12; pores and bars of the inner shell 0.005.

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

Subgenus 2. Tholonilla, Haeckel.

Definition.—Surface of the outer shell covered with radial spines or thorns.

4. Tholonium hexonium, n. sp. (Pl. 10, fig. 17).

Outer shell ellipsoidal, without dome-shaped protuberances, covered with numerous (thirty to fifty) thin and long, bristle-shaped radial spines; network very delicate, irregular, with roundish pores. Inner shell with six marked hemispherical domes of somewhat different sizes; pores regular, circular, with prominent hexagonal frames, twice as broad as the bars; ten to twelve on the basal semicircle of one cupola.

Dimensions.—Major axis of the outer shell 0.15, minor axis 0.14; major axis of the inner shell 0.13, minor axis 0.12; pores 0.008, bars 0.004.

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

5. Tholonium sphæronium, n. sp.

Outer shell very thin walled, spherical, without dome-shaped protuberances, with smooth surface, excepting eight large radial spines, rising from the eight corners of the inner cubical central chamber. Pores of the outer shell very small, subcircular. Inner shell very thick walled, with six marked hemispherical domes; pores subregular, circular, with prominent hexagonal frames, twice as broad as the bars; six to eight on the semicircle of one cupola.

Dimensions.—Diameter of the spherical outer shell 0.15, inner shell 0.11; pores of the inner 0.01, bars 0.005.

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

Genus 299. Cubotholus,^[339] n. gen.

Definition.—Tholonida with simple cortical shell (without external veil), composed of six hemispherical cupolas, opposite in pairs on the poles of three axes perpendicular one to another, covering six sides of the cuboidal Larnacilla-shaped central chamber (with medullary shell).

The genus Cubotholus differs from Tholocubus in the possession of a medullary shell in the central chamber, and may be derived from this genus by its production; but it may also be derived from Staurotholus by apposition of two opposite domes on the flat sides of the cross-shell. Sometimes all six domes are of the same size and form, but commonly different in pairs.

Subgenus 1. Cubotholissa, Haeckel.

Definition.—Surface of the shell smooth or rough, without radial spines.

1. Cubotholus regularis, n. sp. (Pl. 10, fig. 14).

On the six sides of the cubical central chamber six hemispherical cupolas of the same size and form. Surface smooth. Pores regular, circular, twice as broad as the bars; eight in the basal semicircle of each cupola. Medullary shell apparently spherical (?), connected with the eight corners of the central chamber by eight radial beams, regularly disposed. (This species is remarkable for the perfect symmetry of the shell, the six sides of which appear to be quite similar. It differs from the similar Tholocubus regularis in the possession of a medullary shell.)

Dimensions.—Diameter of the cortical shell (equal in all three dimensive axes) 0.15; pores 0.01, bars 0.005; diameter of the medullary shell 0.04.

Habitat.—Pacific, central area, Station 273, depth 2350 fathoms.

2. Cubotholus quadraticus, n. sp.

Surface of the shell smooth. Both principal cupolas (on the poles of the longitudinal axis) larger than the four other cupolas, which have the same size and lie cross-wise in the equatorial plane. (Therefore two of the three fundamental axes equal, the third larger.) Pores subregular, circular, three times as broad as the bars; ten to twelve in the semicircle of each cupola-basis.

Dimensions.—Major axis 0.16, minor axis 0.12; pores 0.012, bars 0.004.

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

3. Cubotholus rhombicus, n. sp.

Surface of the shell smooth. Both principal cupolas (on the poles of the longitudinal axis) larger than the two lateral (on the poles of the transverse axis), and these larger than the two sagittal cupolas (on the poles of the sagittal axis). Therefore all three fundamental axes unequal. Pores irregular, roundish, twice to four times as broad as the bars; eight to twelve in the basal semicircle of each cupola. Medullary shell lentelliptical.

Dimensions.—Major (principal) axis 0.16, middle (lateral) axis 0.14, minor (sagittal) axis 0.12; pores 0.006 to 0.012, bars 0.003.

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

Subgenus 2. Cubotholura, Haeckel.

Definition.—Surface of the shell with radial spines or thorns.

4. Cubotholus octoceras, n. sp.

All six cupolas in pairs of different sizes. Both principal domes larger than the lateral domes, and these larger than the sagittal domes. Pores subregular, circular, twice as broad as the bars; eight to ten in the semicircle of each cupola. From the surface arise (at the intersecting points of every three cupolas) eight strong conical radial spines, about as long as the shell-axis; they lie in two diagonal planes, and are the external free prolongations of eight inner beams (homologous with the eight wing-spines of Tetrapyle octacantha), which connect the lentelliptical medullary shell with the eight corners of the cuboidal central chamber.

Dimensions.—Major axis of the cortical shell 0.15, middle 0.13, minor 0.11; pores 0.008, bars 0.004; diameters of the medullary shell corresponding to 0.05, 0.04, 0.03.

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

Genus 300. Cubotholonium,^[340] n. gen.

Definition.—Tholonida with double (or sometimes triple) cortical shell (with external veil), composed of six hemispherical cupolas, opposite in pairs on the poles of three axes perpendicular one to another, covering six sides of the cuboidal Larnacilla-shaped central chamber (with medullary shell).

The genus Cubotholonium differs from the nearly allied Cubotholus (its probable ancestral form) only in duplication of the cortical shell. I have observed only two species of this rare form, both rather different. In the first species the outer cortical shell forms a simple spherical thin veil around the inner, the six cupolas of which are nearly of the same form and size. In the second species each of the domes of the inner cortical shell is protected by an outer larger cupola, and besides this the whole shell is enveloped by a thin ellipsoidal veil (Pl. 10, fig. 15). Therefore this species may be the representative of a peculiar genus, the most highly developed of all Tholonida—Tholothauma.

1. Cubotholonium sphæroides, n. sp.

Outer cortical shell (or veil) spherical, with smooth surface; network very delicate, with very thin bars and very small irregular, roundish pores. Inner cortical shell simple, composed of six hemispherical cupolas, surrounding the six sides of the cubical central chamber, which encloses a spherical medullary shell (one-third as large as itself). Network of the inner cortical shell regular, with circular pores of the same breadth as the bars, twelve to fourteen in the basal semicircle of one cupola.

Dimensions.—Diameter of the spherical outer shell 0.2, of the inner cortical shell 0.15; pores and bars of the latter 0.006.

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

2. Cubotholonium ellipsoides, n. sp. (Pl. 10, fig. 15).

Tholothauma ellipsoides, Haeckel, 1883, MS.

Outer cortical shell (or veil) ellipsoidal, with very thin irregular network and thorny surface. Inner cortical shell double, with six double, flatly vaulted cupolas, surrounding the six sides of the Larnacilla-shaped central chamber; the double domes of each shell are in opposite pairs somewhat larger than the alternating pairs. Pores subregular, circular, about the same breadth as the bars; eight to twelve in the basal semicircle of one cupola. Central chamber with ellipsoidal medullary shell. Radial spines short, very numerous.

Dimensions.—Major axis of the outer cortical shell 0.28, minor 0.24; major axis of the inner cortical shell 0.16, minor axis 0.14; pores and bars 0.006; medullary shell 0.03.

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

Family XXVIII. Zonarida, n. fam. (Pl. 50, figs. 9-12).

Definition.—Larcoidea with regular, completely latticed cortical shell, distinguished by two to four or more annular constrictions, which lie (all or partly) in the dimensive planes (sagittal, transverse, or lateral), and by which four to eight or more vaulted cupolas or dome-like chambers become separated. In the centre of this chambered cortical shell lies constantly a trizonal or Larnacilla-shaped medullary shell.

The family Zonarida comprises a small number of peculiar Larcoidea, resembling the Tholonida in the composition of the polythalamous cortical shell by a number of cupolas or dome-shaped protuberances. But the disposition and origin of these latter are quite different. Whilst in the Tholonida the axes of the domes are dimensive axes, and these are separated by annular constrictions lying in diagonal planes, in the Zonarida we find the contrary; the axes of the domes are here diagonal axes, and these are separated by annular constrictions lying in dimensive planes. However, this definition agrees absolutely only in the four-chambered Zonarium and in the eight-chambered Zonidium, whilst in the six chambered Zoniscus only four domes are disposed according to this law, two others, however, in the same manner as in the Tholonida. Therefore this genus is intermediate between both families.

The Cortical Shell of the Zonarida is in all cases completely latticed and of regular lentelliptical fundamental form, as in the nearly allied Larnacida and Tholonida. The three dimensive axes are constantly of different sizes, each with two equal poles; commonly (as in the human body) the principal or longitudinal axis is the longest, the sagittal (or dorso-ventral) axis the shortest; the transverse (or lateral) axis being intermediate between them. Of the three dimensive planes the lateral plane is the largest (determined by the principal and transverse axes); the smallest is the equatorial plane (crossed by the transverse and sagittal axes); the sagittal plane (determined by the sagittal and principal axes) being intermediate between them.

The annular constrictions of the cortical shell which produce the dome-shaped protuberances are different in number in the three known genera—two, three, or four. To each constriction often (but not always) corresponds an internal latticed septum, which connects the cortical with the medullary shell. The number of the cupolas is always double the number of the annular constrictions by which they are separated, therefore four, six, or eight.

In all known Zonarida the sagittal septum is quite constant, but derived from the original axial rod, which lies in the principal axis. By ramification of this axial beam and reticular connection with the sagittal girdle arises the sagittal septum, which we found first in Octopyle, halving the four gates of Tetrapyle. Whilst this sagittal septum (between right and left halves of the body) is common to all three known genera of this family, the number and shape of the other annular constrictions are different. In Zonarium (Pl. 50, fig. 9) we find only one transverse constriction (in the equatorial plane), in Zoniscus (figs. 10, 11) two parallel transverse constrictions (parallel to the equatorial plane, on both sides of it). Zonidium (fig. 12) is a combination of both foregoing genera; it has three parallel transverse constrictions (one in the equatorial plane, and one on each side of it).

The Latticed Domes (cupolas or chambers) of the cortical shell exhibit correspondingly a different number and disposition in the three known genera. In Zonarium are found only four crossed chambers, separated by the sagittal and transverse septa; the axes of the four crossed domes are diagonal axes, whilst in the similar Staurotholus they are dimensive axes (principal and transverse axes). In Zonidium we find eight domes, each cupola of Zonarium being halved by a diagonal septum. Zoniscus is intermediate between the two foregoing genera, and has six cupolas, three on each side of the sagittal septum.

The inner communication of the cupolas or chambers is more or less free, the lattice-work of the separating septa between them commonly remaining more or less imperfect, or represented only by some isolated beams or meshes. The outer network of the cupolas is commonly irregular (as in the majority of Larcoidea), but sometimes distinguished by a small number of regularly disposed larger apertures (similar to the "gates" of the Pylonida). From the surface radial spines often arise in characteristic number and symmetrical disposition, commonly as prolongations of the septal axes or of the constricted edges.

The Medullary Shell in all Zonarida is a true trizonal or Larnacilla-shaped lattice-shell (compare above, p. 600); its perimeter (or the first lateral girdle) is sometimes more elliptical, at other times more hexagonal; the hexagon is amphithect; both its lateral sides are often concave and commonly longer than the four other sides.

The Central Capsule in all Zonarida is in a strict geometrical sense a true lentellipsis (compare above, p. 599); its principal axis is commonly one and a third to one and a half times as great as the transverse axis, and twice to three times as great as the sagittal axis. The lentelliptical central capsule encloses the trizonal medullary shell, whilst it is externally enveloped by the chambered cortical shell.

Synopsis of the Genera of Zonarida.

Two annular constrictions and four cupolas, 301. Zonarium.

Three annular constrictions and six cupolas, 302. Zoniscus.

Four annular constrictions and eight cupolas, 303. Zonidium.

Genus 301. Zonarium,^[341] n. gen.

Definition.—Zonarida with four dome-shaped chambers of the cortical shell, separated by two annular constrictions (one sagittal and one transverse).

The genus Zonarium is the most simple form of the Zonarida, and differs from the nearly allied Larnacalpis by two ring-like constrictions, which are crossed at right angles, one in the sagittal (or median) plane, and one in the transverse (or equatorial) plane. By these two annular constrictions four egg-shaped or kidney-shaped chambers become imperfectly separated, which correspond to the quadrants of the lateral plane. The first cause of the marked constrictions may be the formation of the latticed sagittal septum, which is found first in Octopyle, as halving the four gates of Tetrapyle. Between this septum and the constricted narrow transverse girdle the cortical shell grows out in the form of four vaulted cupolas; every two opposite domes are congruent, two neighbouring are symmetrically equal.

1. Zonarium quadrigatum, n. sp.

Cortical shell quadrangular, one and a half times as long as broad, with four rounded corners. Surface thorny, with numerous short radial spines. Sagittal constriction twice as long as the hexagonal medullary shell. Four cupolas kidney-shaped.

Dimensions.—Length of the cortical shell 0.16, breadth 0.11; length of the medullary shell 0.06, breadth 0.04.

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

2. Zonarium quadrispinum, n. sp.

Cortical shell quadrangular, nearly rectangular, about twice as long as broad, with four corners, from which arise four strong, three-sided pyramidal, radial spines (crossed in two diagonals of the lateral plane). Surface thorny, only smooth in the transverse constriction. Sagittal constriction three times as long as the lentelliptical medullary shell. Four cupolas elliptical or nearly quadrangular.

Dimensions.—Length of the cortical shell 0.22, breadth 0.1; length of the medullary shell 0.07, breadth 0.05.

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

3. Zonarium octangulum, n. sp. (Pl. 50, fig. 9).

Cortical shell octangular, one and a fourth times as long as broad, with eight strong conical spines on the eight corners; these are separated by four deep constrictions on the poles of the principal and transverse axes, and by four truncated planes on the poles of the crossed diagonal axes between the former. Sagittal constriction twice as long as the hexagonal medullary shell. Four cupolas kidney-shaped or nearly pentagonal.

Dimensions.—Length of the cortical shell 0.15, breadth 0.12; length of the medullary shell 0.07, breadth 0.04.

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

4. Zonarium tetratholium, n. sp.

Cortical shell quadrangular, with four rounded corners. Surface thorny, with sixteen stronger radial spines; eight of these lie in the lateral plane, in the same symmetrical disposition as in the foregoing species; eight others lie on both sides of the lateral plane, opposite in pairs in two crossed diagonal planes, in the same symmetrical disposition as in Tetrapyle octacantha. Sagittal constriction three times as long as the lentelliptical medullary shell. Four cupolas obliquely elliptical.

Dimensions.—Length of the cortical shell 0.16, breadth 0.12; length of the medullary shell 0.04, breadth 0.03.

Habitat.—North Pacific, Station 241, depth 2300 fathoms.

Genus 302. Zoniscus,^[342] n. gen.

Definition.—Zonarida with six dome-shaped chambers of the cortical shell, separated by three annular constrictions (one sagittal and two transverse, parallel to the equatorial plane).

The genus Zoniscus differs from Zonarium as well as from Zonidium by the development of the transverse girdle, which is not constricted, but on the contrary prominently vaulted in the equatorial plane. Therefore both wings of the transverse girdle form here two opposite lateral or "equatorial cupolas," as in Amphitholus. These are separated from four other domes (the "corner cupolas") by two transverse annular constrictions, which correspond to the free edges of the original transverse girdle. The corner domes of each pair are separated from each other by the sagittal septum.

1. Zoniscus rectangulus, n. sp.

Cortical shell nearly rectangular, with rounded corners, nearly one and a half times as long as broad. Surface thorny, without larger radial spines. Sagittal constriction scarcely half as long as the hexagonal medullary shell. Both equatorial cupolas (or wings of the transverse girdle) scarcely half as large as the four corner cupolas.

Dimensions.—Length of the cortical shell 0.15, breadth 0.11; length of the medullary shell 0.07, breadth 0.045.

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

2. Zoniscus hexathalamus, n. sp.

Cortical shell nearly elliptical, one and a third times as long as broad. Surface nearly smooth, without radial spines. Sagittal constriction three times as long as the lentelliptical medullary shell. Both equatorial cupolas about as large as the four corner cupolas.

Dimensions.—Length of the cortical shell 0.12, breadth 0.09; length of the medullary shell 0.035, breadth 0.025.

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

3. Zoniscus tetracanthus, n. sp. (Pl. 50, fig. 10).

Cortical shell nearly quadrangular, one and a half times as long as broad, with four prominent corners, from which arise in the lateral plane four strong, three-sided pyramidal radial spines (opposite in pairs in two crossed diagonal axes). Surface thorny, with exception of the concave lateral sides. Sagittal constriction two and a half times as long as the hexagonal medullary shell. Both equatorial cupolas scarcely half as large as the four corner cupolas.

Dimensions.—Length of the cortical shell 0.18, breadth 0.12; length of the medullary shell 0.07, breadth 0.04.

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

4. Zoniscus octacanthus, n. sp.

Cortical shell nearly four-sided, prismatic, one and a third times as long as broad, with spiny surface. Eight longer thin radial spines opposite in pairs in two crossed diagonal planes (as in Tetrapyle octacantha). Sagittal constriction two and a half times as long as the hexagonal medullary shell. Both equatorial cupolas somewhat larger than the four corner cupolas.

Dimensions.—Length of the cortical shell 0.16, breadth 0.12; length of the medullary shell 0.055, breadth 0.04.

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

5. Zoniscus hexatholius, n. sp. (Pl. 50, fig. 11).

Cortical shell nearly rectangular, with four rounded corners and deep sagittal constriction, one and a fourth times as long as broad with thorny surface. Twelve longer edged radial spines; eight opposite in pairs in two crossed diagonal planes (as in the foregoing species), four others in the lateral plane, opposite in pairs on both sides of the sagittal constriction, which is scarcely twice as long as the hexagonal, in the equatorial plane constricted medullary shell. Both equatorial cupolas nearly of the same size as the four corner cupolas.

Dimensions.—Length of the cortical shell 0.16, breadth 0.13; length of the medullary shell 0.07, breadth 0.04.

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

Genus 303. Zonidium,^[343] n. gen.

Definition.—Zonarida with eight dome-shaped chambers of the cortical shell, separated by four annular constrictions (one sagittal, one transverse, and two others parallel to the latter).

The genus Zonidium must be regarded as a Zonarium, in which the four cupolas (in the quadrants of the lateral plane) are halved by diagonal beams or latticed septa, lying opposite in pairs in two crossed diagonal planes. Therefore the number of the septa (four) and the domes (eight) is here doubled. Among the eight cupolas we distinguish four median (on both sides of the sagittal plane) and four lateral (on both sides of the equatorial plane); both groups are of different size and form. Probably Zonidium is derived from Zonarium by lattice-connection between the eight diagonal wing-spines, which in both species of this genus are present, the same as in Tetrapyle octacantha.

1. Zonidium octostylium, n. sp.

Cortical shell nearly quadrangular, with rounded corners and thorny surface. Eight long and thin radial spines on both sides of the lateral plane opposite in pairs and lying in two crossed diagonal planes (as in Tetrapyle octacantha). Sagittal constriction three times as long as the lentelliptical medullary shell. Four medial cupolas (on both sides of the sagittal plane) somewhat larger than the four lateral cupolas (on both sides of the equatorial plane).

Dimensions.—Length of the cortical shell 0.15, breadth 0.12; length of the medullary shell 0.05, breadth 0.03.

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

2. Zonidium octotholium, n. sp. (Pl. 50, fig. 12).

Cortical shell nearly octangular, with spiny surface; twenty long and stout radial spines between numerous smaller spines; eight wing-spines opposite in pairs in two crossed diagonal planes (as in the preceding species); twelve other strong spines in the lateral plane (four longer opposite in pairs on the poles of the principal and transverse axes, eight others smaller, alternating between these and the diagonal spines). Sagittal constriction twice as long as the hexagonal medullary shell. Four median cupolas somewhat smaller than the four lateral cupolas.

Dimensions.—Length of the cortical shell 0.18, breadth 0.15; length of the medullary shell 0.07, breadth 0.05.

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

Family XXIX. Lithelida, Haeckel (Pl. 49, figs. 1-7).

Lithelida, Haeckel, 1862, Monogr. d. Radiol., p. 515.

Definition.—Larcoidea with symmetrical spiral shell, divided by the spiral plane into two symmetrical halves; all windings of the spiral lie in this plane. Primordial chamber either simple or Larnacilla-shaped.

The family Lithelida comprises all those Larcoidea in which the growth of the latticed shell is spirally winding in one plane, Nautilus-like. They agree in the spiral growth with the following family. But in the Streblonida the spiral is screw-shaped, ascending (like Helix). Therefore in these latter the geometrical fundamental form of the shell is asymmetrical or "dysdipleural," whereas in the Lithelida bilateral-symmetrical or "eudipleural." The lentelliptical or nearly spherical shell may be divided by a median section into two symmetrical halves; the right half is the mirror image of the left half.

When in 1862 I founded the family Lithelida in my Monograph (p. 515), I knew only one genus, Lithelius, with two species. The rich material of the Challenger collection contains a great number of similar spirally constructed Larcoidea, so that at the present time we may distinguish at least six genera. These belong to two different subfamilies, which may possibly be afterwards better separated as families. The first subfamily, Spiremida, possess a simple, spherical or subspherical, medullary shell; the second subfamily, Larcospirida, possess a trizonal or Larnacilla-shaped medullary shell. No doubt these latter must be derived from Pylonida, as we observe all stages of development starting from a simple Trizonium; but perhaps also the Spiremida have the same origin, their simple, spherical or subspherical, medullary shell being derived from a trizonal or Larnacilla-shaped medullary shell by reduction.

The general appearance in both subfamilies of the Lithelida is quite the same, and it requires a careful study of the medullary shell to distinguish certainly the Spiremida from the Larcospirida. This distinction is often not easy, particularly in the larger forms; the shell is often very opaque and difficult to understand. Only in one position, if the spiral axis be parallel to the axis of the eye of the observer, and the spiral plane be therefore fully seen in the optical plane of the microscope, the spiral line (or the axial section of the latticed spiral lamella) is distinctly observed; in all other positions the figure of the spiral is more or less indistinct, and the whole microscopical image often quite intricate and confused. The sufficient study of this family requires therefore the contemplation of the shell from different sides, and is the more difficult, as the variability of the Lithelida—as of the Pylonida—is extraordinarily great.

The description which I gave of Lithelius (1862) in my Monograph is in some points erroneous, and was afterwards (1879) corrected by R. Hertwig, who explained particularly the near relation of it to Tetrapyle. Indeed the intermediate forms between the Lithelida and the Pylonida are so numerous and so evident in all stages of development, that the derivation of the former (at least of the Larcospirida) from the latter is quite clear. The analogy between the structure of the Lithelida and the calcareous (foraminiferous) Alveolinida is not so complete as I supposed it to be in my Monograph (1862); particularly the formation of the small chambers between the turnings of the spiral lamella is much more complete in the Alveolinida than in the Lithelida.

The cortical shell of all Lithelida has the same geometrical fundamental form as Nautilus or as the nautiloid Polythalamia (Polystomella, Nummulites, &c.); therefore the shell is dipleural, being divided by the median plane into two symmetrical lateral halves. Since the spiral line lies in the median plane, we will call it the spiral plane; it separates the right half from the left. The axis of the body, around which the spiral turns (without touching it), is the spiral axis. The latticed part of the cortical shell, which turns around them, is the spiral lamella. Only in one genus of our family, viz., Tholospira, are the spiral axis, the lateral axis, the spiral plane, and the sagittal plane quite as in Nautilus. In all other genera this disposition is different or is uncertain. This depends on the different part of the cortical shell, from which the spiral growth begins. In this respect we can distinguish four different modes.

In the Larcospirida (or the Lithelida with Larnacilla-shaped medullary shell) the spiral growth exhibits four quite different forms. It begins here with Larcospira, in which already the first cortical girdle of the Diplozonaria determines the spiral growth; one wing of this girdle, the transverse girdle of Amphipyle, grows more swiftly than the other, overgrows it, and thus turns around the principal axis. In Pylospira the first or transverse girdle is already perfectly formed (as in Amphipyle), and the spiral growth is introduced by the second or lateral girdle of Tetrapyle; one wing of it (the right or the left) grows more swiftly than the other, overgrows it, and thus turns around the sagittal axis. In Tholospira also the second girdle is complete, and the spiral growth begins from the third or sagittal girdle. One of its wings grows more swiftly than the other, overgrows it, and thus turns around the transverse axis. Consequently we see that each of the three dimensive planes of the lentelliptical Larcoid-body may be the spiral plane: in Larcospira the transverse plane, in Pylospira the lateral plane, in Tholospira the sagittal plane. Correspondingly the spiral axis in the first genus is the principal, in the second the sagittal, in the third the transverse axis of the central Larnacilla-shell. Therefore in these three genera the spiral plane is the plane of the latticed girdle, which determines the spiral growth, one of both its wings overgrowing the other.

In each of the three above mentioned genera the spiral may be simple or double; it remains simple if only one of both wings of the turning girdle overgrow the other, and this latter remain a simple half girdle (or tube-like wing). Whereas the spiral becomes double if the second wing of the girdle afterwards follow the example of the first wing and now turn around it in the same direction. As this happens in all three genera, we can subdivide them into six subgenera.

A quite peculiar form of spiral growth is produced in Spironium, in which the direction of growth in both lateral wings of the transverse girdle is inverse from the beginning. The left wing grows against the posterior, the right wing against the anterior pole of the principal axis, turning around it in crossed, eight-like spirals. The whole shell afterwards assumes a lentelliptical form.

Commonly between the embracing spiral turnings or convolutions a great number of radial beams is developed, irregularly disposed and often branching; they support the thin spiral lamellæ and give to the whole shell more solidity. Often these beams form imperfect radial septa, by which the spiral cavity of the turnings is divided into a variable number of chambers. But these chambers never become so regular and perfect as in the analogous nautiloid Polythalamia.

In many Lithelida the growth of the shell reaches a certain limit, concluding with the formation of a superficial latticed lamella of lentelliptical or nearly spherical form. In many other forms of the family this seems not to be the case; but these may possibly be younger forms, afterwards reaching the same limit.

The network of the shell in the Lithelida is commonly quite irregular, and so variable that its special conformation has usually no value in the determination of the species. The surface of the shell is often covered with radial spines, which are sometimes arborescent.

The central capsule seems always to preserve the same lentelliptical form (or triaxial ellipsoid) as in all other Larcoidea. With the increase of growth it encloses successively a larger part of the spiral cortical shell, but on the outside is constantly protected by the last turnings of the spiral, or by the lattice-lamella of the surface.

Synopsis of the Genera of Lithelida.

II. Subfamily Spiremida. Central medullary shell simple, spherical or lentelliptical. Surface of the cortical shell smooth or thorny, withou radial spines, 304. Spirema.

Surface of the cortical shell covered with numerous simple or branched radial spines, 305. Lithelius.

II. Subfamily Larcospirida. Central medullary shell double, trizonal or Larnacilla-shaped. The transverse girdle turns around the principal axis, 306. Larcospira.

The lateral girdle turns around the sagittal axis, 307. Pylospira.

The sagittal girdle turns around the transverse axis, 308. Tholospira.

Both wings of the transverse girdle turn around the principal axis in an opposite diagonal direction, 309. Spironium.

I. Subfamily Spiremida. Central medullary shell simple, spherical or lentelliptical.

Surface of the cortical shell smooth or thorny, withou radial spines,

304. Spirema.

Surface of the cortical shell covered with numerous simple or branched radial spines,

305. Lithelius.

II. Subfamily Larcospirida. Central medullary shell double, trizonal or Larnacilla-shaped.

The transverse girdle turns around the principal axis,

306. Larcospira.

The lateral girdle turns around the sagittal axis,

307. Pylospira.

The sagittal girdle turns around the transverse axis,

308. Tholospira.

Both wings of the transverse girdle turn around the principal axis in an opposite diagonal direction,

309. Spironium.

Subfamily 1. Spiremida, Haeckel, 1881, Prodromus, p. 464.

Definition.—Lithelida with simple, spherical or subspherical, medullary shell.

Genus 304. Spirema,^[344] Haeckel, 1881, Prodromus, p. 464.

Definition.—Lithelida with simple, spherical or subspherical, medullary shell, and lentelliptical or subspherical, spirally constructed cortical shell; surface smooth or thorny, without radial spines.

The genus Spirema begins the series of the Spiremida, or of those Lithelida in which the medullary shell presents a simple latticed sphere or ellipsoid, never composed of a double, trizonal or Larnacilla-shaped shell. In the present state of our knowledge we cannot say whether this simple medullary shell be a primary formation, or effected by secondary means, by reduction of a double Larnacilla-shaped medullary shell, which is constantly found in the Larcospirida. The species of this genus (as of all Lithelida) are difficult to distinguish, are transformistic, and incline very much to variations and abnormalities. The spiral may be simple or double.

Subgenus 1. Spiremarium, Haeckel.

Definition.—Spiral convolutions of the cortical shell simple.

1. Spirema lentellipsis, n. sp.

Cortical shell lentelliptical, with smooth surface; proportion of its three dimensive axes = 4 : 5 : 6. In the median plane are visible four perfect turnings of the simple spiral, the breadth of which gradually increases towards the third convolution, finally decreasing; the broadest (third) turning three times as broad as the simple spherical medullary shell.

Dimensions.—Length of the lentelliptical cortical shell 0.18, breadth 0.15, height 0.12; diameter of the spherical medullary shell 0.02.

Habitat.—North Atlantic, Station 353, surface.

2. Spirema melonia, n. sp. (Pl. 49, fig. 1).

Cortical shell nearly spherical, with smooth surface; proportion of its three dimensive axes = 1.4 : 1.5 : 1.6. In the median plane are visible three perfect turnings of the simple spiral, all of the same breadth as the simple spherical medullary shell; the breadth of each convolution somewhat greater at the poles of the principal than at the poles of the sagittal axis.

Dimensions.—Length of the shell 0.16, breadth 0.15, height 0.14; medullary shell 0.018.

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

3. Spirema flustrella, Haeckel.

Flustrella haliomma, Ehrenberg (1861), Abhandl. d. k. Akad. d. Wiss. Berlin, 1872, p. 293, Taf. ii. fig. 6.

Cortical shell egg-shaped, with thorny surface; proportion of its three axes = 4 : 5 : 6. In the median plane are visible three perfect turnings of the simple spiral, the first and second of about the same breadth as the simple spherical medullary shell, the third suddenly increasing, and finally three to four times as broad. Network of the surface irregular, with roundish pores.

Dimensions.—Length of the shell 0.2, breadth 0.17, height 0.14; medullary shell 0.013.

Habitat.—North Atlantic, Greenland, 1000 fathoms, Ehrenberg; Færöe Channel, John Murray.

Subgenus 2. Spiremidium, Haeckel.

Definition.—Spiral convolutions of the cortical shell double.

4. Spirema diplospira, n. sp.

Cortical shell lentelliptical, with smooth surface; proportion of its three dimensive axes = 6 : 7 : 8. In the median plane are visible three perfect turnings of a double spiral, the breadth of which gradually increases; the broadest (third) convolution three times as broad as the simple lentelliptical medullary shell.

Dimensions.—Length of the shell 0.24, breadth 0.21, height 0.18; medullary shell 0.02.

Habitat.—Tropical Pacific, Philippines, Station 200, depth 250 fathoms.

5. Spirema subglobosum, n. sp.

Cortical shell nearly spherical, with thorny surface; proportion of its three axes = 2 : 2.1 : 2.2. In the median plane are visible two perfect turnings of a double spiral, the breadth of which in the second convolution is four times as great as that of the first convolution and the simple spherical medullary shell.

Dimensions.—Length of the shell 0.22, breadth 0.21, height 0.2; medullary shell 0.02.

Habitat.—Tropical Atlantic, off Sierra Leone, Station 348, depth (2450) fathoms.

Genus 305. Lithelius,^[345] Haeckel, 1862, Monogr. d. Radiol., p. 519.

Definition.—Lithelida with simple, spherical or subspherical, medullary shell, and lentelliptical or subspherical, spirally constructed cortical shell; surface covered with numerous, simple or branched, radial spines.

The genus Lithelius, founded by me in 1862, and represented by two Mediterranean species, was at that time the only known form of this family, which now contains six genera and twenty-seven species. It differs from the foregoing Spirema in the possession of numerous radial spines on the surface. These may be either simple or branched. The spiral may be simple or double, and according to this latter modification we distinguish two different subgenera.

Subgenus 1. Lithospira, Haeckel.

Definition.—Spiral convolutions of the cortical shell simple.

1. Lithelius spiralis, Haeckel.

Lithelius spiralis, Haeckel, 1862, Monogr. d. Radiol., p. 519, Taf. xxvii. figs. 6, 7.

Cortical shell lentelliptical, one and a third times as long as broad, covered with very numerous (one hundred to one hundred and fifty or more) simple, bristle-shaped radial spines, about as long as the shell. Spiral turnings simple, all nearly of the same breadth and scarcely broader than the simple spherical medullary shell.

Dimensions.—Length of the cortical shell (with six spiral convolutions) 0.15, breadth 0.13; diameter of the medullary shell 0.012.

Habitat.—Mediterranean, Messina, Haeckel, surface; Atlantic, Stations 348 to 353, surface.

2. Lithelius primordialis, R. Hertwig.

Lithelius primordialis, R. Hertwig, 1879, Organism. d. Radiol., p. 54, Taf. vi. figs. 4, 4a.

Cortical shell subspherical, covered with numerous simple, bristle-shaped radial spines, longer than the shell. Spiral turnings simple, with gradually increasing breadth, so that the beginning of the third spiral is twice as broad as the first and as the simple spherical medullary shell.

Dimensions.—Diameter of the cortical shell (with two spiral convolutions) 0.12; diameter of the medullary shell 0.02.

Habitat.—Mediterranean, Messina, R. Hertwig, surface.

3. Lithelius alveolina, Haeckel, 1862.

Lithelius alveolina, Haeckel, 1862, Monogr. d. Radiol., p. 520, Taf. xxvii. figs. 8, 9.

Cortical shell spherical, covered with simple, very numerous (two hundred to three hundred or more), short, bristle-shaped radial spines, scarcely half as long as the radius of the shell. Spiral turnings simple, with gradually increasing breadth, so that the beginning of the third spiral is three times as broad as the first and as the simple spherical medullary shell.

Dimensions.—Diameter of the cortical shell (with four spiral convolutions) 0.2; diameter of the medullary shell 0.01.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific, on many Stations, surface.

4. Lithelius capreolus, n. sp.

Cortical shell lentelliptical, one and a fourth times as long as broad, covered with numerous (eighty to one hundred and twenty or more) short, branched radial spines, about half as long as the radius of the shell; each spine once or twice dichotomous, with curved divergent branches. Spiral turnings simple, with gradually increasing breadth, so that the beginning of the third spiral is twice as broad as the first, and as the simple spherical medullary shell.

Dimensions.—Length of the cortical shell (with four spiral convolutions) 0.18, breadth 0.14; diameter of the medullary shell 0.015.

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

Subgenus 2. Drymospira, Haeckel, 1881, Prodromus, p. 464.

Definition.—Spiral convolutions of the cortical shell double.

5. Lithelius solaris, n. sp. (Pl. 49, fig. 2).

Cortical shell spherical, covered with simple, very numerous (two hundred to three hundred) bristle-shaped radial spines, longer than the diameter of the shell. Spiral turnings double, both of the same breadth, gradually increasing with the growth of the shell and several times surpassing the diameter of the simple spherical medullary shell. (Pl. 49, fig. 2, exhibits only the first convolutions in the centre of the shell.)

Dimensions.—Diameter of the cortical shell (with four spiral convolutions) 0.18; diameter of the medullary shell 0.02.

Habitat.—Pacific, central area, Stations 266 to 272, surface and in various depths.

6. Lithelius arborescens, n. sp.

Cortical shell lentelliptical, one and a half times as long as broad, covered with numerous (fifty to eighty or more) branched radial spines, about as long as the greatest diameter of the shell; each spine with two to four lateral branches, which are again branched or dichotomous. Spiral turnings double, both of little different breadth, which increases considerably with the growth of the shell, so that the third turn is four times as broad as the simple spherical medullary shell.

Dimensions.—Length of the cortical shell (with three spiral convolutions) 0.18, breadth 0.12; diameter of the medullary shell 0.01.

Habitat.—North Atlantic, Færöe Channel, surface, John Murray.

Subfamily 2. Larcospirida, Haeckel.

Definition.—Lithelida with double, trizonal, or Larnacilla-shaped medullary shell.

Genus 306. Larcospira,^[346] n. gen.

Definition.—Lithelida with double, trizonal, or Larnacilla-shaped medullary shell; cortical shell subspherical or lentelliptical, constructed of a simple or double spiral of the transverse girdle (or primary cortical girdle); the spiral lamella revolving around the principal axis.

The genus Larcospira begins the interesting series of the Larcospirida, or of those Lithelida in which the medullary shell is formed by a trizonal or Larnacilla-shaped lattice-shell, and the cortical shell by spiral turnings of one of the three girdles, which compose the cortical shell of the Pylonida. In Larcospira, as the oldest and most simple form of Larcospirida, the spiral is formed by the transverse girdle, or the first girdle of the Diplozonaria, the only cortical girdle of Amphipyle. If in this genus one of both wings of the transverse girdle grow stronger than the other and overgrow the latter, turning around the principal axis, we reach the characteristic form of Larcospirema, the first subgenus of Larcospira; but if afterwards the second wing follow the example of the first, and overgrow it from the other side, we reach the typical form of the second subgenus, Larcospironium. In this latter subgenus the spiral becomes double, whilst in the former it remains simple.

Subgenus 1. Larcospirema, Haeckel.

Definition.—Spiral convolutions or turns of the cortical shell simple; only one single wing of the transverse girdle turning around the principal axis.

1. Larcospira lentelliptica, n. sp.

Cortical shell with smooth surface, four times as long as the lentelliptical medullary shell. Perimeter of the lateral plane elliptical, one and a half times as long as broad, without constrictions. One lateral wing of the transverse girdle is more strongly developed and turns around the other in two to three simple spiral turns.

Dimensions.—Length of the cortical shell 0.2, breadth 0.16; length of the medullary shell 0.05, breadth 0.04.

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

2. Larcospira quadrangula, n. sp. (Pl. 49, fig. 3).

Cortical shell with thorny surface, three times as long as the lentelliptical medullary shell. Perimeter of the lateral plane nearly quadrangular, with four rounded corners (on the poles of two crossed diagonal axes), one and a third times as long as broad, with one sagittal constriction at the poles of the principal axis. One lateral wing of the transverse girdle turns around the other in one and a half to two simple spiral turns.

Dimensions.—Length of the cortical shell 0.18, breadth 0.14; length of the medullary shell 0.06, breadth 0.04.

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

3. Larcospira sexangula, n. sp.

Cortical shell with spiny surface, four times as long as the hexagonal medullary shell. Perimeter of the lateral plane nearly hexagonal, one and a half times as long as broad, with six rounded corners (two on the poles of the principal axis, four on the poles of two crossed diagonal axes), with three slight ring-like constrictions. One lateral wing of the transverse girdle turns around the other in two to two and a half simple spiral turns.

Dimensions.—Length of the cortical shell 0.24, breadth 0.16; length of the medullary shell 0.06, breadth 0.04.

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

Subgenus 2. Larcospironium, Haeckel.

Definition.—Spiral convolutions or turns of the cortical shell double; both wings of the transverse girdle turning around the principal axis.

4. Larcospira oliva, n. sp.

Cortical shell with smooth surface, six times as long as the lentelliptical medullary shell. Perimeter of the lateral plane elliptical, one and a fourth times as long as broad, without constrictions. Both lateral wings of the transverse girdle turn round one another and form one and a half to two double spiral turns.

Dimensions.—Length of the cortical shell 0.25, breadth 0.2; length of the medullary shell 0.04, breadth 0.035.

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

Genus 307. Pylospira,^[347] n. gen.

Definition.—Lithelida with double, trizonal or Larnacilla-shaped medullary shell; cortical shell subspherical or lentelliptical, constructed of a single or double spiral of the lateral girdle (or second cortical girdle); the spiral lamella revolving round the sagittal axis.

The genus Pylospira follows after Larcospira as the second genus of Larcospirida; but in this latter the spiral of the cortical shell is formed by the transverse girdle (or the first lattice-girdle of the Diplozonaria), whilst in Pylospira it is produced by the lateral girdle, or the second lattice-girdle of that group. Therefore Pylospira may be derived phylogenetically from Tetrapyle in the same manner as Larcospira from Amphipyle. Whilst in this latter the first cause of the spiral turning, the unequal growth of both girdle-wings, proceeds from the transverse girdle, in Pylospira it proceeds from the lateral girdle. One of its wings overgrows the other, turning around the sagittal axis. If the second wing do not become developed, the spiral remains simple and represents the subgenus Pylospirema; but if afterwards the second wing follow the example of the first and overgrow it from the other side, we reach the typical form of the second subgenus, Pylospironium, with a double spiral.

Subgenus 1. Pylospirema, Haeckel.

Definition.—Spiral convolutions or turns of the cortical shell simple, only one single wing of the lateral girdle turning around the sagittal axis.

1. Pylospira tetrapyle, n. sp.

Cortical shell with thorny surface, five times as long as the lentelliptical medullary shell. Perimeter of the lateral plane elliptical, one and a half times as long as broad. Four internal gates (as in Tetrapyle, between the complete lateral wings of the transverse girdle) kidney-shaped. One principal wing of the lateral girdle turns around the other in one and a half to two simple spiral turns.

Dimensions.—Length of the cortical shell 0.21, breadth 0.15; length of the medullary shell 0.04, breadth 0.03.

Habitat.—Pacific, central area, Station 268, depth 2900 fathoms.

2. Pylospira octopyle, n. sp. (Pl. 49, fig. 4).

Cortical shell with thorny surface, three times as long as the lentelliptical medullary shell. Perimeter of the lateral plane elliptical or nearly hexagonal, with four rounded corners (on the poles of two crossed diagonal axes), one and a third times as long as broad. Eight internal egg-shaped gates (as in Octopyle), between the complete lateral wings of the transverse girdle, and two axial beams in the principal axis. One single wing of the lateral girdle turns around the other in two to three simple spiral turns.

Dimensions.—Length of the cortical shell 0.18, breadth 0.14; length of the medullary shell 0.06, breadth 0.035.

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

Subgenus 2. Pylospironium, Haeckel.

Definition.—Spiral convolutions or turns of the cortical shell double; both wings of the lateral girdle turning around the sagittal axis.

3. Pylospira cymbium, n. sp.

Cortical shell with smooth surface, seven times as long as the lentelliptical medullary shell. Perimeter of the lateral plane elliptical, one and a third times as long as broad. Four internal kidney-shaped gates between the complete lateral wings of the transverse girdle (as in Tetrapyle). Both principal wings of the lateral girdle turn round one another in two to two and a half double spiral turns.

Dimensions.—Length of the cortical shell 0.22, breadth 0.17; length of the medullary shell 0.03, breadth 0.025.

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

Genus 308. Tholospira,^[348] n. gen.

Definition.—Lithelida with double, trizonal or Larnacilla-shaped medullary shell; cortical shell subspherical or lentelliptical constructed of a simple or double spiral of the sagittal girdle (or third cortical girdle); the spiral lamella revolving around the transverse axis.

The genus Tholospira represents the third genus of Larcospirida. Whilst the spiral growth of the cortical shell is produced in Larcospira by the first (transverse) girdle of the Diplozonaria, in Pylospira by the second (lateral) girdle, in Tholospira it is effected by the third or sagittal girdle, which we found complete in Pylonium. If in this genus one wing of the sagittal girdle overgrow the other remaining one and turn around the transverse axis, we get Tholospirema, the first subgenus of our genus, with simple spiral; but if afterwards the second wing follow the example of the first, and overgrow it from the other side, we get Tholospironium, with double spiral.

Subgenus 1. Tholospirema, Haeckel.

Definition.—Spiral convolutions or turns of the cortical shell simple, only one single wing of the sagittal girdle turning around the transverse axis.

1. Tholospira nautiloides, n. sp.

Cortical shell with smooth surface, five times as long as the lentelliptical medullary shell. Perimeter of the lateral plane elliptical, one and a half times as long as broad. Four internal kidney-shaped gates (between the lateral wings of the transverse girdle, as in Tetrapyle). One wing of the sagittal girdle turns around the other in two to two and a half simple spiral turns.

Dimensions.—Length of the cortical shell 0.24, breadth 0.18; length of the medullary shell 0.05, breadth 0.04.

Habitat.—Indian Ocean, between Ceylon and Socotra, Haeckel, surface.

2. Tholospira spinosa, n. sp.

Cortical shell covered with numerous (sixty to eighty or more) simple, bristle-like radial spines, about the length of the shell. Perimeter of the lateral plane nearly quadrangular, with four rounded corners (on the poles of two crossed diagonal axes), one and a half times as long as broad. Eight internal egg-shaped gates (between the lateral wings of the transverse girdle and two axial beams in the principal axes, as in Octopyle). One wing of the sagittal girdle turns around the other in two to three simple spiral turns.

Dimensions.—Length of the cortical shell 0.27, breadth 0.18; length of the medullary shell 0.04, breadth 0.03.

Habitat.—South Pacific, Station 288, surface.

3. Tholospira dendrophora, n. sp. (Pl. 49, fig. 6).

Cortical shell covered with numerous (forty to fifty or more) branched radial spines, about half as long as the shell; each spine with two to six dichotomous branches. Perimeter of the lateral plane elliptical, one and a third times as long as broad. Eight internal egg-shaped gates, as in the foregoing species. One single wing of the sagittal girdle turns around the other in three to four spiral turns.

Dimensions.—Length of the cortical shell 0.22, breadth 0.17; length of the medullary shell 0.05, breadth 0.04.

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

Subgenus 2. Tholospironium, Haeckel.

Definition.—Spiral convolutions of the cortical shell double; both wings of the sagittal girdle turning around the transverse axis.

4. Tholospira hystrix, n. sp.

Cortical shell covered with numerous (sixty to eighty or more) simple conical spines, about half as long as the shell. Perimeter of the lateral plane hexagonal, one and a half times as long as broad. Four internal kidney-shaped gates, as in Tetrapyle. Both wings of the sagittal girdle turn round one another in two to two and a half double spiral turns.

Dimensions.—Length of the cortical shell 0.21, breadth 0.14; length of the medullary shell 0.04, breadth 0.03.

Habitat.—North Atlantic, Station 354, surface.

5. Tholospira cervicornis, n. sp. (Pl. 49, fig. 5).

Cortical shell covered with numerous (forty to fifty or more) branched radial spines; each spine antler-shaped, about as long as the medullary Larnacilla-shell, with eight to twelve dichotomous branches (similar to Cromyodrymus abietinus, Pl. 30, fig. 6). Perimeter of the lateral plane elliptical, one and a third times as long as broad. Four internal kidney-shaped gates, as in Tetrapyle. Both wings of the sagittal girdle turn round one another in one and a half to two double spiral turns.

Dimensions.—Length of the cortical shell 0.2, breadth 0.15; length of the medullary shell 0.03, breadth 0.025.

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

Genus 309. Spironium,^[349] n. gen.

Definition.—Lithelida with double, trizonal or Larnacilla-shaped medullary shell; cortical shell subspherical or lentelliptical, constructed of two crossed spirals, which arise from both lateral wings of one girdle (commonly the lateral girdle) and revolve in an opposite diagonal direction around the principal axis.

The genus Spironium differs in a very remarkable manner from all foregoing Lithelida, and is distinguished by a quite peculiar mode of growth. It is most nearly allied to Larcopyle, and may, like this, be derived from Amphipyle (or rather from Larnacilla, beginning to transform into Amphipyle). But whilst in Larcopyle one of the two wings of the lateral girdle overgrows the other in the direction of the transverse axis (turning around the principal axis), here in Spironium both lateral wings begin at the same time to grow out from the lateral sides of the Larnacilla-shaped medullary shell; the most remarkable thing is, however, that the direction of growth in the wings is diverse from the beginning: the left wing grows downwards and turns around the lower (aboral) pole of the principal axis, the right wing grows upwards and turns around the upper (oral) pole of the same axis. Thus both wings of the lateral girdle are crossed in diagonal axes, and with increasing growth one overgrows the other in the direction of these diagonals, so as to resemble the figure 8 in shape. The open gates remaining between the turnings of the girdle become afterwards closed on the surface by irregular lattice-work, and so the whole cortical shell assumes finally a spherical, ellipsoidal, or lentelliptical form. Its surface sometimes becomes covered with simple or branched radial spines. In the interior the eight characteristic egg-shaped gates of Octopyle are commonly (or constantly?) visible, two strong radial beams in the principal axis arising from the poles of the lentelliptical medullary shell.

Subgenus 1. Spironetta, Haeckel.

Definition.—Surface of the shell smooth or rough, but not with radial spines.

1. Spironium octonium, n. sp. (Pl. 49, fig. 7).

Cortical shell lentelliptical, its breadth (or transverse axis) surpassing considerably the length (or the principal axis). Surface thorny and somewhat hump-backed. The spiral wings of the transverse girdle have about the same breadth as the eight internal gates between them and the axial beams.

Dimensions.—Length of the cortical shell (or principal axis) 0.15, breadth (or transverse axis) 0.2; length of the medullary shell 0.05, breadth 0.04.

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

2. Spironium diagonale, n. sp.

Cortical shell nearly spherical, four times as great as the subspherical medullary shell. Surface rough. The spiral wings of the transverse girdle about half as broad as the eight internal gates between them and the axial beams.

Dimensions.—Diameter of the cortical shell 0.16, of the medullary shell 0.04.

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

Subgenus 2. Spironilla, Haeckel.

Definition.—Surface of the shell covered with simple or branched radial spines.

3. Spironium spinosum, n. sp.

Cortical shell subspherical, five times as great as the subspherical medullary shell. Surface covered with numerous (sixty to eighty or more) simple, bristle-like radial spines, longer than the shell. The spiral wings of the transverse girdle of about the same breadth as the eight internal gates between them and the axial beams.

Dimensions.—Diameter of the cortical shell 0.2, of the medullary shell 0.04.

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

4. Spironium arbustum, n. sp.

Cortical shell lentelliptical, its breadth surpassing its length considerably. Surface covered with numerous (forty to sixty or more) thin radial spines, about as long as the greatest diameter of the shell; each spine with two to six lateral branches, which are either simple or again branched (similar to Cromyodrymus abietinus, Pl. 30, fig. 6). The spiral wings of the transverse girdle only half as broad as the eight internal gates between them and the strong beams of the principal axis.

Dimensions.—Length of the cortical shell 0.12, breadth 0.15; length of the hexagonal medullary shell 0.05, breadth 0.04.

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

Family XXX. Streblonida, n. fam. (Pl. 49, figs. 8, 9).

Definition.—Larcoidea with asymmetrical, spiral, polythalamous shell, composed of a variable number of roundish chambers, which form together an ascending spiral; both halves of the shell unequal. Primordial chamber either simple or Larnacilla-shaped.

The family Streblonida comprises those Larcoidea in which a number of chambers is arranged in an ascending spiral, round a simple or trizonal primordial chamber, like winding stairs. They show the same spiral structure as in the foregoing family, but whilst in the Lithelida the spiral line lies in one plane (as in Nautilus), in the Streblonida it ascends like a screw (as in Helix). Therefore the former have the same relation, regarding the spiral structure, to the nautiloid Polythalamia as the latter to the turbinoid Foraminifera. Indeed the single forms of Streblemida repeat in their special structure the characteristic genera of Turbinoida, such as Globigerina, Rosalina, Pulvinulina, Hastigerina, &c. As in these calcareous turbinoid Foraminifera, so also in the analogous siliceous Streblonida the distinction of species is very difficult and open to many objections.

The number of species in this family is very small; all are rare and for the most part very opaque and difficult to understand, so that the following distinction of a dozen species can have only a provisional value. To get a complete idea of their peculiar structure, the shell must be turned and observed from different sides, and thus their full study requires yet much time and work. There are to be found evident transitional forms between them and the Lithelida on the one hand and the Soreumida on the other. Besides this, most species of Streblonida seem to have more inclination to individual varieties and abnormalities than the majority of the other Radiolaria.

The general form of the whole shell is in the Streblonida sometimes more egg-shaped or even subspherical, at other times more top-like or conical, sometimes nearly discoidal. The height of the shell (or the vertical axis of the ascending spiral) is occasionally larger, at other times smaller than the breadth (or the greatest horizontal diameter, perpendicular to the height). Some very flat forms seem to approach the Lithelida. With regard to the internal screw-formation, the shell of all Streblonida is asymmetrical.

The number of the aggregated incomplete chambers is commonly between ten and twenty, but ascends sometimes to thirty, forty, or more. Sometimes the size of all the chambers is nearly the same, sometimes they increase gradually, occasionally also very rapidly. The primordial chamber (or the first and oldest) seems to be commonly the smallest, and inversely, the last and youngest chamber, the largest. But sometimes (in Streblopyle) also the contrary may be the case. The form of the single chambers is very variable, from the spherical or hemispherical through all transitions leading to irregular roundish or longish forms. The network is commonly irregular, with small roundish pores of different sizes, but sometimes also regular, circular. The surface of the shell is commonly smooth or rough, rarely covered with radial spines. In most species the reticulation and particularly the separation of the chambers is more or less incomplete.

As in the Lithelida, so also in the Streblonida we can distinguish two subfamilies. In the Streblacanthida (Streblonia, Streblacantha) the primordial chamber is a simple, spherical, subspherical, or lentelliptical latticed shell. In the Streblopylida (Streblopyle) the primordial chamber is trizonal or Larnacilla-shaped, as in the greater number of Larcoidea, composed of three elliptical latticed girdles of unequal size, perpendicular one to another, and surrounding a simple central chamber. As in the Lithelida, so also here we cannot certainly say whether the former have originated from the latter by reduction of the Larnacilla-shell, or whether both groups be of different origin. The latter is perhaps more probable. This family as well as the foregoing requires a much more careful study than I could give to it.

Synopsis of the Genera of Streblonida.

I. Subfamily Streblacanthida. Primordial chamber simple, spherical or lentelliptical. Shell without radial spines, 310. Streblonia.

Shell with radial spines, 311. Streblacantha.

II. Subfamily Streblopylida. Primordial chamber trizonal or Larnacilla-shaped Shell without radial spines, 312. Streblopyle.

I. Subfamily Streblacanthida. Primordial chamber simple, spherical or lentelliptical.

Shell without radial spines,

310. Streblonia.

Shell with radial spines,

311. Streblacantha.

II. Subfamily Streblopylida. Primordial chamber trizonal or Larnacilla-shaped

Shell without radial spines,

312. Streblopyle.

Genus 310. Streblonia,^[350] n. gen.

Definition.—Streblonida with simple, spherical, subspherical, or lentelliptical primordial chamber, beginning the screw-like series of spirally ascending chambers. Surface smooth or thorny, without radial spines.

The genus Streblonia contains those Streblonida in which a variable number of roundish, subspherical, or longish chambers form a screw-like aggregate, beginning with a quite simple primordial chamber. The special order of the complex spiral offers interesting resemblances to different genera of the calcareous Foraminifera, from which I have taken the corresponding name of the species. The whole form of the shell is sometimes more egg-shaped or subspherical, at other times more top-like or conical, occasionally very flat. Its surface is smooth or rough, but not covered with radial spines.

1. Streblonia globigerina, n. sp.

Shell subspherical, thick walled, clustered, with eight to ten nearly spherical chambers, of rapidly increasing size, the tenth chamber about twelve times as broad as the first. Breadth of the shell nearly equal to the height. Pores subregular, circular, hexagonally formed, of about the same breadth as the bars; about sixteen on the breadth of the tenth chamber. (Resembles very much the common Globigerina.)

Dimensions.—Breadth of the shell 0.18, height 0.16.

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

2. Streblonia uvigerina, n. sp.

Shell nearly egg-shaped, clustered, with eight to eleven subspherical chambers of gradually increasing size, the tenth chamber about six times as broad as the first. Breadth of the shell about half its height. Pores of the shell subregular, circular, about twice as broad as the bars; about twenty on the breadth of the tenth chamber. (Resembles some species of Uvigerina.)

Dimensions.—Breadth of the shell 0.11, height 0.23.

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

3. Streblonia polymorphina, n. sp.

Shell egg-shaped, thin walled, with twelve to fourteen roundish chambers of rapidly increasing size, the tenth chamber about seven times as broad as the first. Breadth of the shell about two-thirds of the height. Pores irregular roundish, twice as broad as the bars; about twenty on the tenth chamber. (Resembles certain forms of Polymorphina.)

Dimensions.—Breadth of shell 0.22, height 0.14.

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

4. Streblonia bulimina, n. sp.

Shell nearly egg-shaped, thick walled, clustered, with fourteen to eighteen egg-shaped chambers of rapidly increasing size, the tenth chamber about eight times as broad as the first. Breadth of the shell about two-thirds of the height. Pores irregular, roundish, half as broad as the bars; about twelve on the breadth of the tenth chamber. (Resembles closely Bulimina.)

Dimensions.—Breadth of the shell 0.17, height 0.24.

Habitat.—Pacific, central area, Station 268, depth 2900 fathoms.

5. Streblonia rosalina, n. sp.

Shell top-shaped or flatly conical, with twelve to sixteen chambers of gradually increasing size, the tenth chamber about four times as broad as the first. Breadth of the shell twice as large as the height. Pores subregular, circular, very small, of the same breadth as the bars; about twelve on the breadth of the tenth chamber. (Resembles some forms of Rosalina.)

Dimensions.—Breadth of the shell 0.27, height 0.13.

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

6. Streblonia planorbulina, n. sp.

Shell very flatly conical, nearly lenticular or discoidal, with twenty to twenty-five chambers of nearly equal size, the tenth chamber a little broader than the first. Breadth of the shell exceeds five to six times the height. Pores subregular, circular, very small, half as broad as the bars; about eight on the breadth of the tenth chamber. (Resembles closely Planorbulina.)

Dimensions.—Breadth of the shell 0.3 to 0.4, height 0.06 to 0.07.

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

7. Streblonia pulvinulina, n. sp.

Shell top-shaped or flatly conical, with thirty to forty chambers of slowly increasing size, the tenth chamber about three times as broad as the first. Breadth of the shell exceeds three times the height. Pores circular, subregular, very small, about one-third as broad as the bars; about thirty in the breadth of the tenth chamber. (Resembles closely Pulvinulina.)

Dimensions.—Breadth of the shell 0.25, height 0.08.

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

Genus 311. Streblacantha,^[351] n. gen.

Definition.—Streblonida with simple, spherical, subspherical, or lentelliptical primordial chamber, beginning the screw-like series of spirally ascending chambers. Surface covered with radial spines.

The genus Streblacantha differs from the nearly allied Streblonia only in the covering of radial spines, and bears therefore the same relation to it as Hastigerina has to Globigerina amongst the similar calcareous Polythalamia.

1. Streblacantha siderolina, n. sp. (Pl. 49, figs. 8, 8a).

Streblonia siderolina, Haeckel, 1883, MS.

Shell flatly conical, with fourteen to sixteen nearly hemispherical chambers of gradually increasing size, the tenth chamber about six times as broad as the first. Breadth of the shell nearly equal to the height. Pores subregular, circular, hexagonally framed, twice as broad as the bars; about nine pores on the breadth of the tenth chamber. Surface covered with numerous short conical radial spines, one-fourth to one-sixth as long as the diameter of the shell.

Dimensions.—Breadth of the shell 0.15, height 0.17.

Habitat.—South Pacific, Station 298, depth 2225 fathoms.

2. Streblacantha calcarina, n. sp.

Shell conical, with sixteen to eighteen roundish chambers of gradually increasing size, the tenth chamber about three times as broad as the first. Breadth of the shell about one and a half times the height. Pores irregular, roundish. Surface covered with numerous strong conical radial spines, about half as long as the diameter of the shell.

Dimensions.—Breadth of the shell 0.24, height 0.17.

Habitat.—South Pacific, Station 285, depth 2375 fathoms.

3. Streblacantha hastigerina, n. sp.

Shell nearly spherical, clustered, with nine to eleven nearly spherical chambers of rapidly increasing size, the tenth chamber about six times as broad as the first. Breadth of the shell nearly equal to the height. Pores subregular, circular, of about the same breadth as the bars. Surface bristly, covered with numerous very thin and long, needle-shaped radial spines, longer than the diameter of the shell. (Resembles closely Hastigerina.)

Dimensions.—Breadth of the shell 0.18, height 0.15.

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

Genus 312. Streblopyle,^[352] n. gen.

Definition.—Streblonida with trizonal lentelliptical medullary shell (composed like Larnacilla of three elliptical dimensive girdles surrounding one simple central primordial chamber). From this begins a screw-like series of spirally ascending chambers. Surface smooth or thorny, without radial spines.

The genus Streblopyle presents externally the same appearance and contour as Streblonia, and is composed like this of a variable number of chambers, ascending screw-like around the axis of the spiral shell. The first or primordial chamber, however, in which the growth begins, is in Streblonia a simple spherical shell, but in Streblopyle a trizonal shell or Larnacilla-shell (compare above, p. 600). The chambers are very incompletely separated, and comparatively much larger, their number much smaller than in Streblonia. The structure in the species of this genus is difficult to understand.

1. Streblopyle helicina, n. sp. (Pl. 49, fig. 9).

Shell helicoid, one and a third times as high as broad, with eight to twelve incomplete semizonal chambers, ascending spirally from the lateral half girdle of the lentelliptical medullary shell, octopyle-shaped, and enveloping it in three to four spiral turnings. The height of the whole cortical shell equals nearly five times the height of the trizonal medullary shell. Pores irregular, roundish. Surface of the shell rough or nearly smooth. (This species seems to be nearly allied to Spironium octonium.)

Dimensions.—Breadth of the spiral cortical shell 0.18, height 0.24; breadth of the medullary shell 0.04, height 0.05.

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

2. Streblopyle spirulina, n. sp.

Shell egg-shaped or nearly spherical, about as high as broad, with eight to nine semizonal chambers, ascending spirally from the subspherical trizonal medullary shell, and enveloping it in four to five turnings. The sixth chamber twice as broad as the trizonal medullary shell. Pores irregular, roundish. Surface of the shell thorny.

Dimensions.—Breadth of the spiral cortical shell 0.27, height 0.25; breadth of the medullary shell 0.05, height 0.06.

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

Family XXXI. Phorticida, Haeckel (Pl. 49, figs. 10, 11).

Phorticida, Haeckel, 1881, Prodromus, p. 464.

Definition.—Larcoidea with quite irregular monothalamous shell, representing irregular modifications of an original lentelliptical latticed shell; the irregular cortical shell encloses a regular or subregular, lentelliptical or trizonal medullary shell.

The family Phorticida comprises a small number of Larcoidea in which a subregular, trizonal, lentelliptical medullary shell is enclosed by an irregular simple or spongy cortical shell. The lattice-work of the latter is sometimes simple and complete, at other times incomplete, with open gates (as in the Pylonida), sometimes also spongy. Its form is always more or less irregular, roundish, often dimply or tuberous; different from most other Larcoidea.

The medullary shell is constantly a regular or subregular Larnacilla-shell, composed of three elliptical latticed girdles of different sizes, perpendicular one to another. This leaves no doubt that the Phorticida are true Larcoidea. The connection of it with the cortical shell is rarely effected by radial beams, commonly by two opposite latticed wings, which are identical with the lateral halves of the transverse girdle in the Pylonida diplozonaria (Amphipyle, Tetrapyle). Often also between this transverse and a second (lateral) girdle there remain large open gates, so that the affinity between these Phorticida and the Pylonida cannot be doubted. In other cases these gates become closed, so that they more nearly approach the Larnacida. From both families they differ by the irregularity of the papillate or tuberous cortical shell. The network is more or less irregular, its surface often thorny, but never covered with symmetrically disposed radial spines.

The central capsule is lentelliptical, encloses the medullary shell, and is enveloped by the cortical shell, as in the nearly allied Pylonida and Larnacida, of which the Phorticida may be regarded as irregular aberrant forms.

Synopsis of the Genera of Phorticida.

Cortical shell simply latticed, 313. Phorticium.

Cortical shell spongy, 314. Spongophortis.

Genus 313. Phorticium,^[353] Haeckel, 1881, Prodromus, p. 464.

Definition.—Phorticida with irregular cortical shell of simple lattice-work, enclosing a lentelliptical Larnacilla-shaped medullary shell.

The genus Phorticium comprises all Phorticida in which the irregular cortical shell is formed by simple lattice-work, not by spongy framework. We can divide this genus into two subgenera: in Phortopyle (as in the Pylonida) the lattice-work of the cortical shell exhibits large openings or gates; in Phortolarcus these gates are perfectly closed by network; the former may be regarded as abnormal or irregular Pylonida, the latter as modifications of Larnacida.

Subgenus 1. Phortopyle, Haeckel.

Definition.—Lattice-work of the irregular cortical shell incomplete, with large openings or gates.

1. Phorticium pylonium, n. sp. (Pl. 49, fig. 10).

Cortical shell irregular, roundish, about three times as large as the enclosed lentelliptical, regular, Larnacilla-shell, connected with it by some radial beams and irregularly latticed girdles; between these remain four to eight large open gates of irregular roundish form and size; and these gates are the same as in Tetrapyle and Octopyle. This very variable species may be regarded as a monstrosity of those genera of Pylonida; it is very common, but all individuals are more or less unequal; some specimens approach to some common species of Tetrapyle. The surface of the shell is more or less spiny.

Dimensions.—Diameter of the irregular cortical shell 0.12 to 0.18; length of the lentelliptical medullary shell 0.05 to 0.06, breadth 0.035 to 0.045.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific, &c., common, surface and in various depths.

2. Phorticium spironium, n. sp.

Cortical shell irregular, roundish, tuberous, about four times as large as the enclosed subregular Larnacilla-shell, connected with it by some irregular radial beams, and by opposite, spirally begining, irregularly latticed girdles, comparable to those of Spironium; between them remain six to twelve large open gates of irregular size and form. Surface rough. The resemblance to some forms of Spironium makes it probable that this species is a deformity or monstrosity of that genus.

Dimensions.—Diameter of the irregular cortical shell 0.12 to 0.2, of the lentelliptical medullary shell 0.03 to 0.06.

Habitat.—Pacific, central area, Stations 270 to 274, surface, and in various depths.

Subgenus 2. Phortolarcus, Haeckel.

Definition.—Lattice-work of the irregular cortical shell complete, without large openings or gates.

3. Phorticium deforme, n. sp.

Cortical shell irregular, roundish or longish, three times as large as the enclosed subregular, lentelliptical Larnacilla-shell, connected with it by two opposite latticed wings (the halves of the transverse girdle of Tetrapyle). Network of the cortical shell irregular, dense, perfectly closed, without larger openings or gates. Surface thorny. (May be regarded as a monstrous form of Larnacalpis.)

Dimensions.—Diameter of the irregular cortical shell 0.15 to 0.18, of the medullary shell 0.04 to 0.06.

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

4. Phorticium abnorme, n. sp.

Cortical shell irregular, roundish, tuberous, with five to ten quite irregular or nearly hemispherical protuberances, which resemble the cupolas of Zonarida. The regular lentelliptical Larnacilla-shell is one-third to one-fourth as large as the enclosing cortical shell, and is connected with it by some irregular radial beams. Lattice-work completely closed, without gates. Surface spiny. (May be regarded as an anomalous form of Zonidium; as in the other species of this variable genus, the individuals are very unequal.)

Dimensions.—Diameter of the irregular cortical shell 0.12 to 0.2, of the medullary shell 0.03 to 0.05.

Habitat.—Atlantic and Pacific, tropical zone, surface, and at various depths.

Genus 314. Spongophortis,^[354] Haeckel, 1881, Prodromus, p. 464.

Definition.—Phorticida with irregular cortical shell of spongy framework, enclosing a lentelliptical Larnacilla-shaped medullary shell.

The genus Spongophortis differs from Phorticium in the spongy framework of the cortical shell. This encloses the inner Larnacilla-shaped medullary shell either directly, or both shells are separated by a hollow interval, and connected either by radial beams or by latticed lamellæ. Perhaps both these subgenera might be better separated as genera.

Subgenus 1. Stypophorticium, Haeckel.

Definition.—Spongy cortical shell immediately enclosing the lentelliptical medullary shell, without hollow interval.

1. Spongophortis spongiosa, n. sp.

Cortical shell irregular, roundish, rough or tuberous, composed of loose spongy framework, which immediately envelops the lentelliptical central Larnacilla-shell; the diameter of the former becomes about five to six times as large as that of the latter.

Dimensions.—Diameter of the spongy cortical shell 0.15 to 0.25, of the trizonal medullary shell 0.03 to 0.04.

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

Subgenus 2. Spongophorticium, Haeckel.

Definition.—Spongy cortical shell separated by a hollow interval from the lentelliptical medullary shell.

2. Spongophortis radiosa, n. sp.

Cortical shell irregular, roundish, four to five times as large as the enclosed lentelliptical Larnacilla-shell, with which it is connected by ten to twenty irregularly disposed radial beams. Spongy framework compact, about as thick as the medullary shell. Surface covered with numerous short, bristle-shaped, radial spines.

Dimensions.—Diameter of the spongy cortical shell 0.15 to 0.2, of the trizonal medullary shell 0.035 to 0.045.

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

3. Spongophortis larnacilla, n. sp. (Pl. 49, figs. 11a-11d).

Cortical shell irregular, roundish, tuberous, three to four times as large as the enclosed lentelliptical Larnacilla-shell, connected with it by two opposite latticed wings (the halves of the transverse girdle of Tetrapyle). Spongy framework compact, about half as thick as the medullary shell. Surface rough. (May be regarded as an abnormal Tetrapyle or Larnacalpis, with an irregular spongy cortical shell.)

Dimensions.—Diameter of the spongy cortical shell 0.16 to 0.2, of the trizonal medullary shell 0.04 to 0.06.

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

Family XXXII. Soreumida, Haeckel (Pl. 49, figs. 12, 13).

Soreumida, Haeckel, 1881, Prodromus, p. 464.

Definition.—Larcoidea with quite irregular polythalamous shell, composed of a variable number of chambers, aggregated without any definite order. Primordial chamber either simple or Larnacilla-shaped.

The family Soreumida contains a small number of Larcoidea, different from most other Sphærellaria in the complete irregularity of the polythalamous shell, which is composed of a variable number of roundish chambers or subspherical latticed shells, aggregated in the form of an irregular heap. We can distinguish in this family only two genera, with very different structure of the central medullary shell or the first chamber beginning the growth; and these correspond to the two subfamilies of the nearly allied Streblonida (p. 704). In Soreuma (as in Streblonia) the first or primordial chamber, from which the growth begins, is like the others, a simple spherical or irregular roundish lattice-shell. In Sorolarcus, however (as in Streblopyle), the first or primordial chamber is a trizonal or Larnacilla-shell. It is not improbable that the former originated phylogenetically from Streblonia, the latter from Streblopyle, by loss of the original spiral order of growth. But it is also possible that these groups have no nearer relation. Among the calcareous Foraminifera a very similar form is represented by Acervulina and its allies.

The general form of the whole shell in the Soreumida is sometimes more egg-shaped or lentelliptical, at other times even subspherical, occasionally quite irregular, tuberous, or clustered. The number of the aggregated chambers is very variable, in Sorolarcus between ten and thirty, in Soreuma ascending to fifty to eighty, sometimes from one hundred to one hundred and fifty and more. Their size is sometimes nearly equal, at other times very different, their form commonly very irregular, roundish, but sometimes also subspherical or egg-shaped. The network of the shell is also commonly irregular, with roundish pores of different sizes. The surface is usually smooth or rough, rarely covered with radial spines.

The central capsule is not known, as I observed only a few skeletons of this family.

Synopsis of the Genera of Soreumida.

Primordial chamber of the shell simple, subspherical or roundish, 315. Soreuma.

Primordial chamber of the shell trizonal or Larnacilla-shaped, 316. Sorolarcus.

Genus 315. Soreuma,^[355] Haeckel, 1881, Prodromus, p. 464.

Definition.—Soreumida with numerous chambers, aggregated without any regularity around one simple, spherical or subspherical, central chamber.

The genus Soreuma contains those Soreumida in which no trace of any regular structure is found, but all the chambers of the irregular shell are without any order, aggregated around a simple spherical or subspherical central chamber or medullary shell. Soreuma may have originated either from Sorolarcus by loss of the central Larnacilla-shell or from Cenolarcus by irregular apposition of new chambers around the lentelliptical central chamber or simple Larcoid-shell. Some species seem to exhibit a transition to Sorolarcus. Owing to the absolute irregularity of the polythalamous shell Soreuma resembles Acervulina among the Foraminifera.

Subgenus 1. Soreumium, Haeckel.

Definition.—Shell without radial spines.

1. Soreuma irregulare, n. sp. (Pl. 49, fig. 12).

Shell irregular, clustered, or tuberous, composed of a large number (one hundred and twenty to one hundred and fifty or more) of irregular, roundish chambers of very different sizes, the largest four to five times as broad as the smallest. Network very delicate, with very small roundish pores, to five times as broad as the bars. Surface thorny.

Dimensions.—Diameter of the shell 0.3, of the single chambers 0.02 to 0.08.

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

2. Soreuma acinosum, n. sp.

Shell irregularly lentelliptical, with different growth in the three dimensions, composed of a large number (forty to sixty or more) of irregular, roundish chambers of very different sizes, the largest six to eight times as broad as the smallest. Pores subregular, circular, twice as broad as the bars. Surface smooth.

Dimensions.—Length of the shell 0.21, breadth 0.17, height 0.13; diameter of the largest chambers 0.03, of the smallest 0.004.

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

3. Soreuma subglobosum, n. sp.

Shell nearly spherical, composed of a variable number (twelve to fifteen or more) of irregularly aggregated subspherical chambers of nearly equal size. Pores subregular, circular, twice as broad as the bars. Surface thorny.

Dimensions.—Diameter of the shell 0.25, of the largest chambers 0.04, of the smallest 0.005.

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

4. Soreuma acervulina, n. sp.

Shell quite irregular, cloddy, or tuberous, composed of twenty to thirty (or more) roundish chambers of almost uniform size, the largest twice to three times as broad as the smallest. Pores irregular, roundish. Surface smooth.

Dimensions.—Diameter of the shell 0.18 to 0.24, of the largest chambers 0.06, of the smallest 0.02.

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

Subgenus 2. Soreumidium, Haeckel.

Definition.—Shell with radial spines.

5. Soreuma spinosum, n. sp.

Shell quite irregular, cloddy, or tuberous, composed of thirty to forty subspherical chambers of nearly the same size. Pores subregular, circular, twice as broad as the bars; on the equator of each chamber six to eight pores. Surface thorny, covered with irregularly scattered conical radial spines, about as long as the diameter of the chambers.

Dimensions.—Diameter of the shell 0.17 to 0.25, of the chambers 0.04.

Habitat.—North Pacific, Station 241, depth 2300 fathoms.

6. Soreuma setosum, n. sp.

Shell nearly spherical, composed of sixty to seventy (or more) irregular, roundish chambers of very different sizes, the largest five to six times as broad as the smallest. Pores irregular, roundish. Surface bristly, covered with very numerous, long and thin, bristle-shaped radial spines, about as long as the diameter of the shell.

Dimensions.—Diameter of the shell 0.28, of the chambers 0.005 to 0.03.

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

Genus 316. Sorolarcus,^[356] n. gen.

Definition.—Soreumida with numerous chambers, aggregated irregularly around a trizonal medullary shell or Larnacilla-shell.

The genus Sorolarcus comprises those Soreumida in which the heap of irregularly aggregated chambers encloses a central trizonal medullary shell, by which they demonstrate clearly their descent from Larnacida or Pylonida. The lentelliptical medullary shell exhibits quite the same characteristic structure as that of Larnacilla, being composed of three elliptical latticed girdles, perpendicular one to another. In some species also the beginning of a second system of girdles is clearly indicated, so that there can be no doubt as to their derivation from Amphipyle or Tetrapyle.

Subgenus 1. Sorolarcium, Haeckel.

Definition.—Shell without radial spines.

1. Sorolarcus larnacillifer, n. sp. (Pl. 49, fig. 13).

Shell irregular, clustered, or tuberous, composed of twenty to thirty irregular, roundish chambers of very different size, the largest four to eight times as broad as the smallest, aggregated without order around a central, lentelliptical, Larnacilla-shaped medullary shell. Pores irregular, roundish, twice to four times as broad as the bars. Surface smooth or a little spiny.

Dimensions.—Diameter of the whole shell 0.18, of the central Larnacilla-shell 0.05.

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

2. Sorolarcus tetrapylifer, n. sp.

Shell irregularly roundish, clustered, composed of ten to twelve irregular rather long chambers of almost uniform size, the largest twice as broad as the smallest, aggregated without order around a central shell of the structure of Tetrapyle, which encloses an inner trizonal Larnacilla-shell of half the size. Pores irregular, roundish, twice to four times as broad as the bars. Surface spiny.

Dimensions.—Diameter of the whole shell 0.25, of the outer (Tetrapyle-like) medullary shell 0.12, of the inner (Larnacilla-like) shell 0.06.

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

Subgenus 2. Sorolarcidium, Haeckel.

Definition.—Shell with radial spines.

3. Sorolarcus terminalis, n. sp.

Shell nearly spherical, composed of fifteen to eighteen irregularly aggregated roundish chambers of nearly equal size; in the centre a lentelliptical Larnacilla-shell. Surface covered with numerous thin, bristle-like radial spines, somewhat longer than the shell.