5. Triolena trigonalis, n. sp.
Arm-chambers nearly triangular, at the base half as broad as the circular central chamber, at the concave lunulate distal end twice as broad, and armed with four conical radial spines (two on each side of the equatorial plane). Surface thorny.
Dimensions.—Diameter of the shell 0.05, of the central chamber 0.015.
Habitat.—Central Pacific, Station 271, depth 2425 fathoms.
Genus 246. Triopyle,[[285]] Haeckel, 1881, Prodromus, p. 464.
Definition.—Pylodiscida with a simple, spherical or lenticular, central chamber, surrounded by three simple arm-chambers. Notches between the three arms transformed into gates by a connecting equatorial girdle.
The genus Triopyle differs from the preceding Triolene in the development of a simple ring or latticed equatorial girdle, which connects the distal ends of the three arm-chambers, and transforms the open notches between them into three gates. The ring may be circular, triangular, or hexagonal.
1. Triopyle circulus, n. sp.
Disk circular, three times as broad as the hexagonal central chamber. Three arm-chambers trapezoidal, at the convex distal end as broad, at the base half as broad as the three circular gates between them. Surface smooth. No marginal spines on the girdle.
Dimensions.—Diameter of the disk 0.045, of the gates 0.015.