Habitat.—North Pacific, south of Japan, Station 237, surface
3. Pylodiscus cardiopylus, n. sp.
Cortical shell hexangular, equilateral, five times as broad as the triangular, Triopyle-shaped medullary shell. Surface smooth. Three arms triangular, at the distal end as broad as the three heart-shaped gates. On the margin six strong pyramidal spines in the equatorial plane (adradial, as prolongations of the lateral arm-edges).
Dimensions.—Diameter of the disk 0.15, of the gates 0.05.
Habitat.—Indian Ocean, Sunda Strait, Rabbe.
4. Pylodiscus nephropylus, n. sp.
Cortical shell circular, three times as broad as the circular, Triopyle-shaped medullary shell. Surface spiny. Three arms trapezoidal, half as broad as the three kidney-shaped gates. On the margin twelve stronger, conical, radial spines, opposite in pairs on both sides of the disk, disposed in six pairs at the distal end of the arms.
Dimensions.—Diameter of the disk 0.2, of the medullary shell 0.06.
Habitat.—Central Pacific, Station 268, depth 2900 fathoms.