Definition.—Collosphærida with simple shells, on the inside with radial centripetal beams.
The genus Tribonosphæra differs from Collosphæra by a very peculiar and rare character, the development of centripetal radial sticks on the internal face of the shell; these beams are not united in the centrum, but finish freely in a certain distance from it.
1. Tribonosphæra centripetalis, n. sp. (Pl. [5], fig. 12).
Shell roundish or subspherical, with numerous small circular or roundish pores, about twice as broad as the bars. Twenty to thirty pores on the half meridian of the shell. Outside of the shell smooth, inside a variable number (ten to twenty) of thin, radial, centripetal sticks or spines, one-third or one-half as long as the radius of the shell. (In the central capsule many very large crystals, resting after the destruction of the capsule.)
Dimensions.—Diameter of the shell 0.1 to 0.12, of the pores 0.003 to 0.005, of the bridges 0.001 to 0.002; length of the inner centripetal sticks 0.02 to 0.03.
Habitat.—Central Pacific, Station 271, surface.
Genus 31. Pharyngosphæra,[[53]] n. gen.
Definition.—Collosphærida with simple shells, having on the inside radial centripetal tubes, the walls of which are solid.
The genus Pharyngosphæra differs from Collosphæra by the development of radial tubules on the inside of the shell, which are directed centripetally towards its centre. The wall of the tubule is solid, not latticed as in the following genus.
1. Pharyngosphæra stomodæa, n. sp. (Pl. [5], fig. 10).