Synopsis of the Genera of Tholonida.

Subfamily 1. Amphitholida, Haeckel.

Definition.—Tholonida with monaxial growth; cupolas opposite on the poles of one axis. (Shell commonly three-chambered, with two domes on both sides of the central chamber.)

Genus 289. Tholartus,^[328] n. gen.

Definition.—Tholonida with simple cortical shell (without external veil); with two hemispherical cupolas, opposite on the poles of one axis; central chamber between them simple (without medullary shell).

The genus Tholartus (Pl. 10, fig. 1) represents the most simple form of all Tholonida, a three-jointed simple cortical shell without medullary shell; two hemispherical cupolas or domes are attached on both lateral sides of a simple triaxial ellipsoidal central chamber, corresponding to the poles of its lateral or transverse axis. Tholartus may be regarded as the common ancestral form of all Tholonida, and may be derived either from the Pylonida Monozonium (by complete lattice-locking of the lateral wings) or from the Ellipsida Cenellipsis (by development of two lateral protuberances on the poles of the transverse axis). But it is also possible that the absence of the medullary shell is produced by reduction, and in this case Tholartus may be descended from Amphitholus.

Subgenus 1. Tholartella, Haeckel.

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

1. Tholartus tricolus, n. sp. (Pl. 10, fig. 1).

Central chamber one and a half times as high and as broad as both cupolas. Surface of the shell rough. Pores regular, circular, without hexagonal frames, three times as broad as the bars; about sixteen on the half meridian of the central chamber (or its vertical diameter).

Dimensions.—Length of the shell (major axis of the central chamber, vertical) 0.1, breadth of the shell (major axis of the whole three-chambered shell, horizontal) 0.13; pores 0.01, bars 0.003.

Habitat.—Pacific, central area, Station 270, depth 2925 fathoms.

2. Tholartus paniscus, n. sp.

Central chamber of the same breadth, but of the double height of both cupolas. Surface of the shell rough. Pores regular, circular, with hexagonal frames, of the same breadth as the bars; eight to ten on the half meridian of the central chamber.

Dimensions.—Length of the shell (major axis of the central chamber, vertical) 0.12, breadth of the shell (major axis of the whole three-chambered shell, horizontal) 0.15; pores and bars 0.008.

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

3. Tholartus isocolus, n. sp.

Central chamber of the same breadth and height as both cupolas. Surface of the shell smooth. Pores irregular, roundish, once to three times as broad as the bars; ten to fifteen on the half meridian of the central chamber.

Dimensions.—Length of the shell 0.11, breadth 0.14; pores 0.004 to 0.01, bars 0.003.

Habitat.—Pacific, central area, Station 270, depth 2925 fathoms.

Subgenus 2. Tholartissa, Haeckel.

Definition.—Surface of the shell with radial spines.

4. Tholartus tripanis, n. sp.

Central chamber of the same size as both cupolas. Surface of the shell thorny, everywhere covered with short conical radial spines, about as long as the cupolas. Pores regular or subregular, circular, twice as broad as the bars; eight to ten on the half meridian.

Dimensions.—Length of the shell 0.1, breadth 0.12; pores 0.01, bars 0.005.

Habitat.—South Pacific, Station 295, surface.

5. Tholartus sagitta, n. sp.

Central chamber twice as large as both cupolas. Surface of the shell spiny, with eight to twelve regularly (?) distributed radial spines, radiating from the two constrictions between the three chambers. Spines needle-shaped, very thin and long. Pores subregular or irregular, roundish or circular, about three times as broad as the bars; twelve to sixteen on the half meridian.

Dimensions.—Length of the shell 0.11, breadth 0.15; pores 0.01, bars 0.003.

Habitat.—North Pacific, Station 244, surface.

Genus 290. Tholodes,^[329] n. gen.

Definition.—Tholonida with double cortical shell (with external veil), with two hemispherical cupolas, opposite on the poles of one axis; central chamber between them simple (without medullary shell).

The genus Tholodes (Pl. 10, fig. 2) differs from Tholartus, its probable ancestral form, only in the duplication of the shell; the outer shell has exactly the same three-jointed form as the inner; both are connected by eight radial beams, lying in two diagonal planes and corresponding to the eight frontal spines of Tetrapyle octacantha. Possibly Tholodes may also be descended from Amphitholonium by loss of the medullary shell. I have observed only one single specimen of this genus.

1. Tholodes cupula, n. sp. (Pl. 10, fig. 2).

Outer shell of the same form and structure as the inner shell. Central chamber larger than both cupolas. Surface a little rough, without radial spines. Distance of both shells equals the height of the outer cupolas. Pores of both shells regular, circular, three times as broad as the bars; six to seven in the semicircle of one inner cupola, ten to twelve in the semicircle of one outer cupola. Both shells are connected by eight radial beams, crossed in two diagonal planes.

Dimensions.—Major axis of the outer shell 0.1, minor 0.065; major axis of the inner shell 0.05, minor 0.04; pores 0.006, bars 0.002.

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

Genus 291. Amphitholus,^[330] n. gen.

Definition.—Tholonida with simple cortical shell (without external veil), with two hemispherical cupolas, opposite on the poles of one axis; central chamber (between them) Larnacilla-shaped, with medullary shell.

The genus Amphitholus is the most simple form of all Coccotholida (or all Tholonida provided with medullary shell). Its simple cortical shell exhibits, like Tholartus, two lateral hemispheric cupolas, attached on both sides of a lentelliptical central chamber (on the poles of its transverse axis). The central chamber has the form of a triaxial ellipsoid, and contains, like Larnacilla, a small medullary shell, connected with it by the wings of a latticed transverse girdle. Amphitholus may be derived either from Tholartus by secondary production of a cortical shell, or (more probably) from Larnacilla by apposition of two lateral dome-shaped protuberances. In the latter case it may be regarded as an Amphipyle, the lateral open wings of which are closed by lattice-work.

Subgenus 1. Amphitholissa, Haeckel.

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

1. Amphitholus artiscus, n. sp. (Pl. 10, fig. 3).

Central chamber of the same height as both cupolas. Surface of the cortical shell rough. Pores regular, circular, with prominent hexagonal frames, twice as broad as the bars; eight to ten in the basal semicircle of one cupola.

Dimensions.—Major axis of the shell 0.16, minor axis 0.1; pores 0.008, bars 0.004.

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

2. Amphitholus artidium, n. sp.

Central chamber one-fourth higher than both cupolas. Surface of the cortical shell smooth. Pores irregular, roundish, once to three times as broad as the bars. (Very similar to Tholartus tricolus, Pl. 10, fig. 1, but different by the medullary shell.)

Dimensions.—Major axis of the shell 0.15, minor axis 0.12; pores 0.004 to 0.01, bars 0.003.

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

Subgenus 2. Amphitholura, Haeckel.

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

3. Amphitholus octacanthus, n. sp.

Central chamber about twice as high and broad as both cupolas. From the surface arise, symmetrically distributed, eight stout conical radial spines, lying in two diagonal planes, as prolongations of the eight wing-beams, which connect the Tetrapyle-shaped medullary shell with the two ring-like constrictions of the cortical shell. Pores of the latter regular, circular, twice as broad as the bars; ten to twelve in the basal semicircle of one cupola.

Dimensions.—Major axis of the shell 0.15, minor 0.12; pores 0.01, bars 0.005.

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

4. Amphitholus dodecanthus, n. sp.

Central chamber a little larger than both cupolas. From the surface arise twelve strong conical radial spines, four on the poles of the major and the minor axis of the shell, lying in the lateral plane; eight others lying in two diagonal planes, as prolongations of the eight wing-beams, which connect the Tetrapyle-shaped medullary shell with the two ring-like constrictions of the cortical shell. Pores of the latter irregular, roundish, twice to four times as broad as the bars; sixteen to eighteen in the basal semicircle of one cupola.

Dimensions.—Major axis of the shell 0.15, minor 0.11; pores 0.004 to 0.008, bars 0.002.

Habitat.—North Pacific, Station 256, surface.

5. Amphitholus acanthometra, n. sp. (Pl. 10, figs. 5, 6).

Central chamber about twice as broad and as high as both cupolas. On the surface quite symmetrically distributed twenty long and strong cylindrical radial spines; eight in the sagittal plane or in the meridian plane of the central chamber (four opposite in pairs in the principal and the sagittal axes, four others in the middle between the principal and the sagittal spines); four in the horizontal transverse plane, on both sides of the poles of the major or lateral axis; and eight in diagonal planes (corresponding to the eight wing-spines of Tetrapyle octacantha). In the centre of the central chamber is a distinct trizonal medullary shell like that of Tetrapyle, with two vertical columella beams. Pores of the cortical shell subregular, circular, with elevated hexagonal frames, about four times as broad as the bars; five to seven in the semicircle of one cupola. (This remarkable species differs from Tholartus vicenus in the possession of a medullary shell, from Amphitholonium acanthometra by the simple cortical shell. Compare these species).

Dimensions.—Major axis of the shell 0.14 to 0.16, minor axis 0.10 to 0.12; pores 0.015, bars 0.004; major axis of the medullary shell 0.04 to 0.05, minor (horizontal) axis 0.02 to 0.03; length of the twenty radial spines 0.18 to 0.24, basal breadth 0.01.

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

6. Amphitholus armatus, n. sp.

Central chamber twice as broad, but of the same height, as the flat vaulted cupolas. Surface armed with thirty to forty very large three-sided prismatic spines, longer than the major axis of the shell. Pores irregular, roundish, twice to five times as broad as the bars; eight to nine on the basal semicircle of one cupola.

Dimensions.—Major axis of the shell 0.15, minor axis 0.1; pores 0.006 to 0.015, bars 0.003; length of the spines 0.2 to 0.25, breadth 0.01.

Habitat.—North Atlantic, Station 353, surface.

7. Amphitholus polyacanthus, n. sp.

Central chamber of the same breadth and height as both cupolas. Surface armed with very numerous (sixty to eighty) strong conical spines, about as long as the minor axis of the shell. Pores subregular, circular, twice as broad as the bars; sixteen to eighteen in the basal semicircle of one cupola.

Dimensions.—Major axis of the shell 0.13, minor 0.08; pores 0.006, bars 0.003; length of the radial spines 0.09, breadth 0.006.

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

8. Amphitholus panicium, n. sp. (Pl. 10, fig. 4).

Central chamber ellipsoidal, nearly twice as broad, but of the same height, as both cupolas. Whole surface thorny; the largest radial thorns about as long as the medullary shell. Pores irregular, roundish, twice to four times as broad as the bars. On the base of each cupola a circle of ten to twelve larger square pores, separated by radial beams, which are prolonged into stouter free spines. This remarkable formation of the cupolas, very rare in this family, recalls the characteristic formation of the distal chambers of the Panartida and Zygartida (e.g., Pl. 40, figs. 4, 8, &c.), where it is very common.

Dimensions.—Major axis of the shell 0.15, minor 0.1; pores 0.005 to 0.012, bars 0.003; large square pores 0.02; axes of the medullary shell 0.03 and 0.02.

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

Genus 292. Amphitholonium,^[331] n. gen.

Definition.—Tholonida with double cortical shell (with external veil), with two hemispherical cupolas, opposite on the poles of one axis; central chamber (between them) Larnacilla-shaped, with medullary shell.

The genus Amphitholonium differs from the nearly allied Amphitholus (probably its ancestral form) only in the duplication of the cortical shell; the outer has the same three-jointed form as the inner, and is connected with it by a variable number of radial beams. From the similar Tholodes it differs in the possession of a medullary shell.

1. Amphitholonium tricolonium, n. sp. (Pl. 10, fig. 7).

Outer cortical shell smooth, of the same three-jointed form as the inner, at an equal distance from it throughout the whole circumference; central chamber higher-vaulted than both cupolas. Network of the outer shell delicate, with subregular, circular pores. Pores of the thick-walled inner shell subregular, circular, with hexagonal frames, three times as broad as the bars; eight to ten in the basal semicircle of one cupola.

Dimensions.—Major axis of the outer cortical shell 0.2, minor axis 0.15; major axis of the inner cortical shell 0.16, minor axis 0.11; pores 0.01, bars 0.0035.

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

2. Amphitholonium octostylium, n. sp.

Outer cortical shell lentelliptical, smooth, not articulated, at a varying distance from the three-jointed inner shell; central chamber of the latter twice as high as both hemispherical cupolas. Network of the outer shell very thin, cob-web like. Pores of the inner shell subregular, roundish, twice as broad as the bars; six to seven in the semicircle of one cupola. Eight thin and long, bristle-shaped, radial spines, opposite in pairs in two crossed diagonal planes.

Dimensions.—Major axis of the outer cortical shell 0.16, minor 0.12; major axis of the inner cortical shell 0.12, minor 0.09; pores 0.01, bars 0.005.

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

3. Amphitholonium acanthonium, n. sp.

Outer cortical shell of the same three-jointed form as the inner, at a uniform distance from it; central chamber higher vaulted than both cupolas. Network of the outer shell irregular, delicate, of the inner regular, strong, with circular, hexagonally framed pores, three times as broad as the bars; eight to nine in the semicircle of one cupola. On the surface, quite symmetrically disposed, twenty long and strong, cylindrical, radial spines; eight in the sagittal plane, four in the transverse plane; eight in two diagonal planes between the former and the latter. The remarkable geometric disposition of the twenty spines is in this species quite the same as in Amphitholus acanthometra. It differs from this nearly allied species in the double cortical shell.

Dimensions.—Major axis of the outer cortical shell 0.18, minor 0.14; major axis of the inner cortical shell 0.14, minor 0.1; pores 0.012, bars 0.004.

Habitat.—South Pacific, Station 295, surface.

Subfamily 2. Staurotholida, Haeckel.

Definition.—Tholonida with diaxial growth; cupolas crossed in pairs, opposite on the poles of two axes, perpendicular one to another. (Shell commonly five-chambered, with four domes, cross-wise surrounding the central chamber.)

Genus 293. Tholostaurus,^[332] 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 simple (without medullary shell).

The genus Tholostaurus is the most simple form of the Staurotholida, or the Tholonida with four crossed hemispherical cupolas, lying on the poles of two axes perpendicular one to another. The central chamber communicates by four wide openings with the four domes, and contains no medullary shell. Tholostaurus may originate either from Tholartus by apposition of two opposite cupolas between the first pair, or from Staurotholus by loss of the medullary shell.

Subgenus 1. Tholostaurantha, Haeckel.

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

1. Tholostaurus quadrigatus, n. sp.

All four cupolas nearly of the same size and form, subregular. Surface smooth, without radial spines. Pores subregular, circular, four times as broad as the bars; eight to ten pores in the basal semicircle of one cupola.

Dimensions.—Diameter of the shell 0.12; pores 0.008, bars 0.002.

Habitat.—Pacific, central area, Station 272, surface.

2. Tholostaurus cruciformis, n. sp.

Two opposite cupolas larger than the two others. Surface rough, without radial spines. Pores regular, circular, hexagonally framed, twice as broad as the bars; twelve to fourteen in the basal semicircle of one cupola.

Dimensions.—Major axis of the shell 0.16, minor axis 0.12; pores 0.006, bars 0.003.

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

Subgenus 2. Tholostauroma, Haeckel.

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

3. Tholostaurus tetrabelonis, n. sp.

All four cupolas nearly of the same size and form, subregular. Pores regular, circular, hexagonally framed, twice as broad as the bars; twelve to fourteen in the semicircle of one cupola. Four long and stout conical radial spines, two vertical on the poles of the principal axis, two horizontal on the poles of the transverse axis.

Dimensions.—Major axis of the shell 0.15, minor 0.13; pores 0.006, bars 0.003.

Habitat.—South Pacific, Station 288, surface.

4. Tholostaurus octobelonis, n. sp.

Two opposite cupolas larger than the two others. Pores subregular, circular, three times as broad as the bars; ten to twelve in the semicircle of one cupola. Eight long and thin, needle-shaped, radial spines, in pairs crossed in two diagonal planes.

Dimensions.—Major axis of the shell 0.16, minor 0.12; pores 0.01, bars 0.003.

Habitat.—South Pacific, Station 291, surface.

5. Tholostaurus dodecabelos, n. sp.

Two opposite cupolas larger than the two others. Pores irregular, roundish, twice to three times as broad as the bars; six to eight in the semicircle of one cupola. Twelve thin and long radial spines, four on the poles of the two crossed axes (principal and lateral), eight crossed in two diagonal planes.

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

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

6. Tholostaurus polybelonis, n. sp.

Two opposite cupolas larger than the two others. Pores circular, hexagonally framed, of the same breadth as the bars; ten to twelve in the semicircle of one cupola. Numerous (twenty to thirty or more) thin, bristle-like, radial spines, about as long as the radius of the shell.

Dimensions.—Major axis of the shell 0.15, minor axis 0.12; pores and bars 0.007.

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

Genus 294. Tholoma,^[333] 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 simple (without medullary shell).

The genus Tholoma (Pl. 10, figs. 10, 13) differs from the preceding Tholostaurus (its probable ancestral form) only in the duplication of the shell. The outer (secondary) shell has the same cross-form as the inner (primary) shell. In the two observed species the growth seems to be different, in the first species all four cupolas of each cross being of the same size, form, and age; in the second two opposite cupolas, larger and apparently older than the other two. Tholoma is possibly the offspring of Staurotholonium, from which it may have been produced by loss of the medullary shell.

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).