Definition.—The connecting staffs between both shells are hollow tubes (derived from Siphonosphæra).
1. Clathrosphæra circumtexta, n. sp. (Pl. [8], 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. [8], 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.