Definition.—Thorax with a variable number (ten to twenty or more) radial ribs, prolonged into free terminal feet.
10. Acanthocorys dodecaster, n. sp.
Cephalis small, subspherical, with small circular pores and a large conical horn of twice the length, and some accessory spines. Thorax thorny, flatly campanulate, with twelve stout curved ribs, which at the peristome are prolonged into twelve slender, curved feet of twice the length; four of them are centrifugal prolongations of the four cortinar beams separating the four large meshes of the collar septum; eight other ribs are secondary, interpolated in pairs between the former. At the base of the thorax are twelve large triangular holes between the ribs; the other network is irregular, with polygonal meshes.
Dimensions.—Cephalis 0.03 diameter, thorax 0.05 long, 0.12 broad.
Habitat.—Central Pacific, Station 271, depth 2425 fathoms.
11. Acanthocorys polypodia, n. sp.
Cephalis small, hemispherical, with small, roundish pores and divergent radial spines. Thorax flatly conical, spiny, with twenty to twenty-four divergent, straight ribs, which in the proximal third are separated by the same number of large, triangular meshes, in the middle third connected by irregular network, in the distal third free.
Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.06 long, 0.15 broad.
Habitat.—Central Pacific, Station 273, depth 2350 fathoms.