Phacoid shell three times as broad as the medullary shell, with seven pores on its radius, surrounded by two to three perfect chambered rings. Arms nearly square, scarcely as long and nearly as broad as the diameter of the central disk, at the rounded distal end armed with a very strong, pyramidal, terminal spine, longer than the arm itself, and at the base as broad as the medullary shell.
Dimensions.—Diameter of the phacoid shell 0.09, of the medullary shell 0.03; length of the arms 0.08, breadth 0.1.
Habitat.—Pacific, central area, Station 265, depth 2900 fathoms.
Genus 209. Stauractura,[[248]] Haeckel, 1881, Prodromus, p. 459.
Definition.—Coccodiscida with four chambered arms on the margin of the circular or quadrangular disk, crossed in two equatorial diameters, connected by a spongy patagium.
The genus Stauractura differs from the foregoing in the patagium between the arms, and bears therefore the same relation to it as Histiastrum in the Porodiscida does to Stauralastrum. All known species of this genus form a regular square, if we connect the end points of the arm axes by lines.
Subgenus 1. Stauracturium, Haeckel.
Definition.—Distal end of the arms blunt or truncated, without terminal spines.
1. Stauractura octogona, n. sp.
Phacoid shell twice as broad as the medullary shell, with eight pores in its radius. Arms nearly square, little larger than the phacoid shell, with broad truncated distal ends. The corners of the latter are so connected by the complete patagium, that the whole shell forms a regular octagon.