Page:Scientific results HMS Challenger vol 18 part 2.djvu/120

996 2. Toxarium subcirculare, n. sp.

Galear and thoracal bows simple, armed with scattered simple spines of about equal size, smaller than the smooth frontal bows between them. Sagittal constriction very flat. Therefore the frontal perimeter of the shell is nearly circular.

Dimensions.—Length of the shell 0.15, breadth 0.14.

Habitat.—North Atlantic (Antilles), Weber, surface.

3. Toxarium thorax, n. sp. (Pl. 93, fig. 18).

Galear bows simple, smaller than the frontal bows, and these again smaller than the simple thoracal bows; therefore the shell increases in breadth towards the base, and resembles the skeleton of the thorax of one of the higher vertebrates (the bow-pairs corresponding to rib-pairs, the ventral part of the sagittal ring to the sternum, the dorsal part to the vertebral column). Sagittal constriction very deep. All bows are armed with scattered, irregularly branched spines.

Dimensions.—Length of the shell 0.17, breadth 0.2.

Habitat.—Central Pacific, Station 265, depth 2900 fathoms.

4. Toxarium constrictum, n. sp.

Galear and thoracal bows simple, of nearly equal size, larger than the frontal bows between them. Therefore the shell is constricted in the equatorial plane. Sagittal constriction also deep. All bows armed with scattered, irregularly branched spines.

Dimensions.—Length of the shell 0.14, breadth 0.12.

Habitat.—North Pacific, Station 236, surface.

Definition.—Galear bows simple, thoracal bows forked.

5. Toxarium cordatum, n. sp. (Pl. 93, fig. 19).

Galear bows simple, thoracal bows forked, both somewhat smaller than frontal bows; all bows armed with scattered simple conical spines, mostly developed at the thoracal bows. Both galear bows are united in a central vertical columella, which arises from the apex of the sagittal ring, and is prolonged into an apical horn. Therefore the sagittal constriction exists only in the basal half of the inversely cordate shell.

Dimensions.—Length of the shell 0.18, breadth 0.16.

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