Page:Scientific results HMS Challenger vol 18 part 2.djvu/754

1630 be derived from it by elevation of the hexagonal pyramids, which in the latter lie in the spherical plane).

Dimensions.—Diameter of the sphere 4.4; pyramidal tubes 0.25 long, 0.01 broad.

Habitat.—Indian Ocean, Cocos Islands (Rabbe), surface.

10. Auloscena serrata, n. sp. (Pl. 110, fig. 5).

Radial tubes spindle-shaped, tapering towards both ends, thorny, twice as long as the thorny pyramidal tubes; armed at the distal end with an elegant corona which is composed of twelve to sixteen curved terminal branches. Each branch bears two opposite series of small recurved teeth and a terminal spathilla of six to eight larger recurved teeth.

Dimensions.—Diameter of the sphere 3.0; pyramidal tubes 0.3 long, 0.012 broad.

Habitat.—South Pacific, Station 298, depth 2225 fathoms.

Definition.— with triangular meshes in the network, the tubes of which are connected in different directions, and form the spongy wall of a spherical shell. Radial tubes arise on the surface at the nodal points.

The genus Auloplegma, one of the rarest forms of Aulosphærida, differs from the preceding genera in the spongy structure of the lattice-sphere, the thickened wall of which is composed of a loose framework. Numerous tubes, irregularly disposed in different directions, are connected at the nodal points of this loose spongy framework, whilst radial tubes arise on the surface of the latter. Auloplegma exhibits therefore a relation to Aulosphæra, its probable ancestral form, similar to that which Plegmosphæra does to Acanthosphæra among the.

1. Auloplegma perplexum, n. sp. (Pl. 111, figs. 8, 8a).

Radial tubes straight, cylindro-conical, armed with six to eight verticils of lateral branches, which increase in size towards the base; each verticil is a cross of four dichotomous delicate ramules, ending with a spinulate knob. The length of the radial tube is about equal to the radial diameter of the spongy framework, which forms the thick wall of the spherical shell, and is composed of smooth and straight cylindrical tubes.

Dimensions.—Diameter of the shell 1.5 to 2.0, of its wall 0.3 to 0.4; length of the radial tubes 0.2 to 0.3, basal breadth 0.015.

Habitat.—North Pacific, Station 237, surface.