Page:Scientific results HMS Challenger vol 18 part 1.djvu/776

568 1. Pylolena inermis, n. sp.

Arms club-shaped, at the base half as broad, at the rounded distal end as broad as the triopyle-shaped medullary shell. Surface and margin smooth.

Dimensions.—Diameter of the cortical shell 0.15, of the medullary shell 0.05.

Habitat.—Equatorial Atlantic, Station 347, surface; Central Pacific, Station 272, surface.

2. Pylolena armata, n. sp. (Pl. 48, fig. 15).

Arms trapezoid, at the base half as broad, at the distal end twice as broad as the triopyle-shaped medullary shell. Surface and margin thorny. Twelve strong conical spines at the distal end of the three arms, two opposite on both faces of the arm-edges.

Dimensions.—Diameter of the cortical shell 0.2, of the medullary shell 0.06.

Habitat.—South Atlantic, Station 325, surface.

Definition.— with triopyle-shaped medullary shell, surrounded by three distal arm-chambers. Notches between the three arms transformed into gates by a connecting equatorial girdle.

The genus Hexapyle differs from the preceding Pylolene in the development of an equatorial ring or latticed girdle, which connects the free extremities of the three distal ends and transforms the open notches between them into gates. It simulates therefore the formation of Triopyle, from which it differs by duplication of the arm-joints and of the gates (in each radius occur one proximal and one distal gate).

1. Hexapyle triangula, n. sp.

Cortical shell triangular, with three rounded corners, three times as broad as the triangular triopyle-shaped medullary shell. Surface smooth or rough, but not spiny. Three arms two-thirds as broad as the three egg-shaped gates of each side.

Dimensions.—Diameter of the cortical shell (or length of one side of the triangle) 0.15, of the medullary shell 0.05; breadth of the gates 0.06, of the bridges between them 0.04.

Habitat.—Pacific, central area, Station 272, depth 2600 fathoms.

2. Hexapyle sexangula, n. sp.

Cortical shell hexagonal, with six equal sides, four times as broad as the triangular triopyle-shaped medullary shell. Surface rough, but not spiny. Three arms (on their smallest part) half as broad as the three triangular gates (on their broadest part).