Page:Scientific results HMS Challenger vol 18 part 2.djvu/387

Rh large, triangular or ovate basal holes between the six ribs. Three of these ribs are primary or perradial, and arise immediately from the collar septum, alternating with three secondary or interradial ribs, which arise more outside. The specimen observed by me exhibited six apical horns, and was more complete than that figured by Bütschli, the six ribs being prolonged over the connecting lattice-girdle into six short, divergent feet.

Dimensions.—Cephalis 0.06 long, 0.06 broad; thorax 0.08 long, 0.1 broad.

Habitat.—Fossil in Barbados.

Definition.—Thorax with nine divergent ribs or radial beams, three of which are primary or perradial, the other six secondary or interradial.

5. Acanthocorys umbellifera, Haeckel.

Arachnocorys umbellifera, Haeckel, 1862, Monogr. d. Radiol., p. 305, Taf. vi. fig. 12.

Cephalis large, ovate, with subregular, circular pores and numerous divergent, simple spines of different lengths. Thorax flatly conical, with nine strong, divergent ribs, which in the distal half are free, in the proximal half connected by numerous transverse beams, forming irregular polygonal meshes. Dorsal face of the thorax armed with scattered ascending spines.

Dimensions.—Cephalis 0.05 long, 0.035 broad; thorax 0.05 long, 0.12 broad.

Habitat.—Mediterranean (Messina); Atlantic, Station 354, surface.

6. Acanthocorys triloba, n. sp.

Cephalis large, campanulate, trilobed, with irregular, roundish pores, numerous spines, and a large pyramidal horn on the top, which is connected by three constricted arches with the base of the horizontal collar beams. From the latter arise as centrifugal prolongations three stout, curved, primary ribs of the flatly vaulted thorax, and each of these gives off at the base two opposite, lateral, secondary ribs. These nine ribs are spiny, and connected by irregular, arachnoidal network.

Dimensions.—Cephalis 0.05 long, 0.07 broad; thorax 0.08 long, 0.18 broad.

Habitat.—Central Pacific, Station 272, depth 2600 fathoms.

7. Acanthocorys enneapodia, n. sp.

Cephalis large, ovate, with irregular roundish pores, and numerous divergent, ascending spines. Thorax smooth, conical, little larger, with the same network, and nine larger, triangular holes at the base; with nine straight, equally-disposed ribs, which are prolonged into slender feet twice the length. With these latter alternate nine shorter radial spines, arising from the truncate peristome.

Dimensions.—Cephalis 0.05 long, 0.04 broad; thorax 0.05 long, 0.09 broad.

Habitat.—Tropical Atlantic, Station 348, depth 2450 fathoms.