Page:Scientific results HMS Challenger vol 18 part 2.djvu/46

922 thin convex bow. In this way arises a very simple, equilateral triangular skeleton, with three equal large meshes.

Dimensions.—Length of the spines 0.14, sides of the triangle 0.16.

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

2. Triplecta triactis, n. sp. (Pl. 91, fig. 7).

Spines straight, equal, three-sided prismatic, pinnate, each with three to four pairs of opposite slender pinnulæ or lateral branches; the pinnulæ of each spine are correspondingly parallel to the main rods of the other two spines. All pinnulæ branched and connected by a few slender bows, marking the sides of a regular triangle.

Dimensions.—Length of the spines 0.15, sides of the triangle 0.17.

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

Definition.— with three radial spines, arising from one common central point and corresponding to the edges of a three-sided pyramid.

The genus Plectophora has been derived from Plagiacantha by union of the meeting neighbouring branches of the three radial spines, and exhibits therefore to it the same relation that Triplecta bears to Triplagia. The loose framework so produced corresponds to the three sides of a flat pyramid and supports the central capsule.

1. Plectophora triomma, n. sp.

Spines equal, straight, three-sided prismatic, thorny, connected by three convex bows, the meeting branches of lateral spines arising in one pair from the middle part of each spine. Therefore the skeleton exhibits three large ovate meshes only.

Dimensions.—Length of the spines 0.12, of the meshes 0.08.

Habitat.—North Pacific, Station 238, surface.

2. Plectophora arachnoides, Haeckel.

Plagiacantha arachnoides, var., Claparède, 1858, Études sur les Infusoires et les Rhizopodes, p. 462, Taf. xxii. fig. 9.

Spines straight, cylindrical, trifid, with one pair of lateral branches. The nine diverging, straight, and smooth branches are connected in the distal part by slender concave bows, so that the whole skeleton exhibits nine wide meshes, three larger pentagonal and six smaller triangular.

Dimensions.—Length of the spines 0.14, of their branches 0.07.

Habitat.—North Atlantic, west coast of Norway (Claparède), surface.