Definition.—Shell with seventy to one hundred or more funnel-shaped dimples, each of which opens on the bottom by one aperture or by a couple of pores; twenty larger dimples in the centre of the plates (each with a couple of pores, sometimes also three couples) and fifty to one hundred or more smaller dimples, each of which contains one sutural pore. No blind dimples between the perforated dimples.
1. Hystrichaspis pectinata, n. sp. (Pl. [138], fig. 8).
Shell with numerous (one hundred to two hundred?) funnel-shaped dimples, each of which is pierced at the bottom by one or two pores; twenty larger dimples in the centre of the plates (each with two aspinal pores), and fifty to one hundred and fifty or more smaller dimples (each with one sutural pore). No blind dimples. Crests between the dimples armed with a continuous series of simple by-spines. Radial main spines stout, in the inner half cylindrical, in the outer conical, more or less compressed.
Dimensions.—Diameter of the shell 0.13, of the pores 0.004 to 0.006.
Habitat.—Tropical Atlantic, Station 352, surface.
2. Hystrichaspis furcata, n. sp. (Pl. [138], fig. 9).
Shell with numerous (one hundred to two hundred?) funnel-shaped dimples, each of which is pierced at the bottom by one or two pores; twenty larger dimples in the centre of the plates (each with two large aspinal pores), and fifty to one hundred and fifty or more smaller dimples (each with one small sutural pore). No blind dimples. Crests between the dimples armed with forked by-spines. Radial main spines stout, leaf-shaped, tapering towards both ends.
Dimensions.—Diameter of the shell 0.12, parmal pores 0.01, sutural pores 0.005.
Habitat.—Central Pacific, Station 276, surface.
3. Hystrichaspis cristata, n. sp. (Pl. [138], fig. 11).