Dimensions.—Diameter of the sphere 5.0, of the meshes 0.2; breadth of the bars 0.015.
Habitat.—Indian Ocean, Madagascar (Rabbe), surface.
8. Aulastrum polyceros, n. sp.
Radial tubes spindle-shaped, tapering from the broader middle towards both ends, spiny, twice as long as the spiny tangential tubes, armed at the distal end with a corona of twelve to twenty divergent curved teeth (similar to the radial tubes of Auloscena tentorium, Pl. [110], fig. 6). Meshes irregular, polygonal, very variable in size and form. All tubes of this species are armed with scattered, short, conical spines.
Dimensions.—Diameter of the sphere 4.5, of the meshes 0.1 to 0.2; breadth of the bars 0.006.
Habitat.—Central Pacific, Station 271, depth 2425 fathoms.
Genus 690. Aulodictyum,[[309]] Haeckel, 1879, Sitzungsb. med.-nat. Gesellsch. Jena, Dec. 12, p. 6.
Definition.—Aulosphærida with polygonal meshes in the network, the tubes of which are connected in different directions and form the spongy wall of a spherical shell. No radial tubes prominent over the surface.
The genus Aulodictyum differs from Aulonia, its ancestral form, in the development of a spongy framework in the thickened wall of the spherical lattice-shell. It bears therefore to the latter the same relation as Auloplegma does to Aularia. But the outer surface of the hollow sphere is in Aulodictyum completely smooth, as well as the inner, and bears no radial tubes. Only one species of this genus has been observed.
1. Aulodictyum hydrodictyum, n. sp.