4. Clistophæna armata, n. sp. (Pl. 57, fig. 7).
Shell spiny, with deep collar stricture. Length of the two joints = 4 : 18, breadth = 5 : 15. Cephalis subspherical, with small, circular, hexagonally-framed pores, and a stout, three-sided prismatic, cuspidate horn of the same length. Thorax pear-shaped, with regular, circular pores and three pairs of stout pyramidal wings, placed in the three primary meridional planes of the collar beams; three of them lie in the upper, and three in the lower third of the thorax. Margin of the flat base with nine cylindrical, somewhat club-shaped, divergent feet.
Dimensions.—Cephalis 0.04 long, 0.05 broad; thorax 0.18 long, 0.15 broad.
Habitat.—Central Pacific, Station 266, depth 2750 fathoms.
5. Clistophæna enneolena, n. sp.
Shell spiny, with sharp collar stricture. Length of the two joints = 4 : 20, breadth 5 : 16. Cephalis hemispherical, hyaline, with a stout conical horn of the same length and some small accessory horns. Thorax ovate, spiny, with subregular, circular pores. Margin of the vaulted base with nine divergent, conical feet, half as long as the thorax.
Dimensions.—Cephalis 0.04 long, 0.05 broad; thorax 0.2 long, 0.16 broad.
Habitat.—South Pacific, Station 296, depth 1825 fathoms.
6. Clistophæna polyolena, n. sp.
Shell smooth, conical, with obliterated collar stricture. Length of the two joints = 1 : 5, breadth = 2 : 5. Cephalis hemispherical, with small, circular pores and two divergent conical horns (a major occipital and a smaller frontal horn). Thorax obtusely conical, with regular, hexagonal pores at the mantle, and circular pores in the basal plate, the margin of which bears eighteen vertical, parallel, conical feet, as long as the cephalis.
Dimensions.—Cephalis 0.015 long, 0.025 broad; thorax 0.08 long, 0.08 broad.
Habitat.—Central Pacific, Stations 271 to 274, depth 2350 to 2750 fathoms.
Family LXIV.—Sethocyrtida, n. fam.
Sethocorida et Sethocapsida, Haeckel, 1881, Prodromus, pp. 439, 433.
Definition.—Dicyrtida eradiata. (Cyrtoidea with a two-jointed shell, divided by a transverse constriction into cephalis and thorax, without radial apophyses).
The family Sethocyrtida, composed of the Sethocorida and Sethocapsida of my Prodromus, comprises those Cyrtoidea in which the shell is two-jointed and bears no radial apophyses. The two subfamilies differ in the shape of the mouth, which in the Sethocorida is a simple wide opening, and in the Sethocapsida is closed by a lattice-plate. The former are here divided into eight, the latter into three genera.
