Subfamily Clathrosphærida, Haeckel, 1881, Prodromus, p. 472

Definition.—Collosphærida with a double lattice-shell around every central capsule of the cœnobium; both concentric shells connected by irregular or subradial beams, commonly solid or lamellar staffs, rarely hollow tubes.

Genus 43. Clathrosphæra, Haeckel, 1881, Prodromus, p. 472.

Definition.—Collosphærida with a double lattice-shell around every central capsule of the cœnobium; surface of the outer shell smooth.

The genus Clathrosphæra (with smooth surface) and the following Xanthiosphæra (with spiny surface) form together the small subfamily, Clathrosphærida, different from the other Collosphærida by the double lattice-shell. From the surface of the inner primary shell arise either solid spines or hollow tubes, which unite by the anastomosis of irregular branches and so form the outer secondary shell, often very incomplete and irregular. All Clathrosphærida seem to inhabit great depths.

Subgenus 1. Clathrosphærula, Haeckel.

Definition.—The connecting staffs between both shells are hollow tubes (derived from Siphonosphæra).

1. Clathrosphæra circumtexta, n. sp. (Pl. , fig. 6).

Inner shell spherical, with irregular roundish large meshes, now broader now smaller than their bars. Eight to ten meshes in the half meridian of the shell. All these meshes are prolonged into short cylindrical hollow tubes, about as long as broad, somewhat constricted in the middle. From the margins of the outer openings of these tubes proceed very numerous and delicate siliceous filaments, which all lie on the same spherical face, branch, anastomose, and twine over the openings and the intervals between them, forming a very thin, arachnoid spherical outer shell. The meshes of this are quite irregular polygonal, of very different size and form. The radius of the inner shell bears to that of the outer a ratio = 5 : 6.

Dimensions.—Diameter of the inner shell 0.11 to 0.13, of the outer 0.13 to 0.16; meshes of the inner shell 0.005 to 0.02, of the outer 0.005 to 0.04.

Habitat.—North Pacific, Stations 238 to 253, depths 2050 to 3950 fathoms.

Subgenus 2. Clathrosphærium, Haeckel.

Definition.—The connecting staffs between the two shells are solid rods or lamellar spines (derived from Acrosphæra).

2. Clathrosphæra arachnoides, n. sp. (Pl. , fig. 7).

Inner shell spherical, with irregular roundish meshes, two or three times as broad as the bars. Ten to twelve meshes in the half meridian of the shell. From its surface arise numerous conical radial spines (with base often fenestrated), which at equal distances from the surface send out lateral branches. All these branches lie on a spherical face, and form by communications the irregular, very delicate, arachnoid network of the outer shell, quite unlike that of the inner, with large polygonal meshes of very different size. Eight to sixteen meshes in the half meridian of the shell. Surface of the outer shell nearly spherical, somewhat uneven, like a spider's web. The radius of the inner shell bears to that of the outer a ratio = 3 : 4.

Dimensions.—Diameter of the inner shell 0.12 to 0.14, of the outer 0.15 to 0.18; pores of the inner shell 0.003 to 0.02, of the outer 0.01 to 0.04.

Habitat.—Central area of the Tropical Pacific, Station 268, depth 2900 fathoms.

3. Clathrosphæra lamellosa, n. sp. (Pl. , fig. 8).

Inner shell spherical or subspherical, with irregular roundish meshes, about half as broad as the bars. Twelve to sixteen meshes in the half meridian of the shell. From its surface arise numerous oblique irregular staffs or broad and thin lamellæ, which branch quite irregularly, and by communications of the branches form the thin outer shell. This is quite irregular roundish or subspherical, very unlike the inner, with large polygonal meshes of different size, six to twelve in the half meridian of the shell. Bridges between the meshes very variable, now very thin filamentous, now very broad lamellar. Outer surface very uneven or tuberculated, but not spinous. The radius of the inner shell bears to that of the outer a ratio = 5 : 6.

Dimensions.—Diameter of the inner shell 0.1 to 0.13, of the outer 0.12 to 0.18; pores of the inner shell 0.003 to 0.009, of the outer 0.01 to 0.04.

Habitat.—Central area of the Tropical Pacific, Stations 270 to 274, depths 2350 to 2925 fathoms.

Genus 44. Xanthiosphæra, Haeckel, 1881, Prodromus, p. 472.

Definition.—Collosphærida with a double lattice-shell around every central capsule of the cœnobium; surface of the outer shell thorny or spiny.

The genus Xanthiosphæra differs from the foregoing Clathrosphæra by spines or thorns arising from the surface of the outer shell, commonly very irregular.

1. Xanthiosphæra capillacea, n. sp.

Inner shell spherical, with irregular polygonal meshes, three to five times as broad as their narrow bars. Six to eight meshes in the half meridian of the shell. From its surface arise at the nodes of the network numerous thin radial spines, which, at equal distances from the surface, send out lateral branches. All these branches lie on a spherical face, and form by communications the irregular delicate network of the outer shell, very like that of the inner, with large polygonal meshes, six to eight meshes in the half meridian of the shell. Surface of the outer shell covered with numerous straight spines, prolongations of the inner spines, but only half as long as these. The radius of the inner shell bears to that of the outer a ratio = 3 : 5.

Dimensions.—Diameter of the inner shell 0.1 to 0.12, of the outer 0.15 to 0.19; pores of the inner shell 0.02 to 0.04 to 0.06, of the outer 0.04 to 0.06 to 0.08; length of the outer spines 0.01 to 0.02.

Habitat.—Central area of the Tropical Pacific, Station 263, depth 2650 fathoms.

2. Xanthiosphæra erinacea, n. sp. (Pl. , fig. 9).

Inner shell spherical, with irregular roundish meshes, one-half to two times as broad as the bars. Fifteen to twenty meshes in the half meridian of the shell. From its surface arise numerous thin radial spines, which at equal distances from the surface send out lateral branches. All these branches lie on the face of a sphere, and form by communications the irregular delicate network of the outer shell, very unlike that of the inner, with large polygonal meshes, twelve to twenty-four in the half meridian of the shell. Surface of the outer shell covered with numerous straight spines, prolongations of the inner spines, and of the same length. The radius of the inner shell bears to that of the outer a ratio = 3 : 4.

Dimensions.—Diameter of the inner shell 0.1 to 0.12, of the outer 0.13 to 0.16; pores of the inner shell 0.002 to 0.008, of the outer 0.01 to 0.03; length of the outer spines 0.02 to 0.03.

Habitat.—Central area of the Tropical Pacific, Stations 270, 272, depth 2925 and 2600 fathoms respectively.

3. Xanthiosphæra lappacea, n. sp. (Pl. , figs. 10, 11).

Inner shell spherical or subspherical, with very small roundish pores, quite irregularly scattered, one-fourth to three-fourth as broad as their bars. Ten to twenty pores in the half meridian of the shell. From its surface arise in an extremely irregular and variable manner numerous oblique spines, often curved, often lamellar, and perforated by pores, sometimes hollow, fenestrated cones. At different distances from the surface these spines send out lateral curved branches, which by communications form the delicate and very irregular network of the outer shell. This network is often incomplete and very unlike that of the inner shell, with large polygonal meshes, six to eighteen in the half meridian of the shell. Surface of the outer shell covered with numerous small, curved, and oblique spines, prolongations of the inner spines, but scarcely one-third to one-half as long as these. The radius of the inner shell bears to that of the outer a ratio = 3 : 4.

Dimensions.—Diameter of the inner shell 0.08 to 0.12, of the outer 0.11 to 0.15; pores of the inner shell 0.001 to 0.009, of the outer 0.01 to 0.04; length of the outer spines 0.005 to 0.009.

Habitat.—Central area of the Tropical Pacific, Stations 263 to 274, depths 2350 to 3000 fathoms.