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, 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. , 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. , 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, 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. , 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. , 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, 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. , 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, 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. , 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. , 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.