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, 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, 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. , 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. , 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, n. sp. (Pl. , 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, 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. , 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. , 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, 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. , 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.