Habitat.—South Pacific, Station 288, surface.
Genus 241. Pentinastrum,[[280]] Haeckel, 1881, Prodromus, p. 461.
Definition.—Porodiscida with five simple, undivided, chambered arms, connected by a patagium.
The genus Pentinastrum differs from the foregoing Pentalastrum only in the development of a patagium or connecticulum between the arms, and bears therefore the same relation to it that Histiastrum does to Stauralastrum, or Hymeniastrum to Dictyastrum.
1. Pentinastrum asteriscus , n. sp. (Pl. [44], fig. 2).
All arms equal, twice as long as broad, at their base two-thirds as broad as at their truncated distal end, which bears a strong, pyramidal, terminal spine. Each arm is divided by five transverse septa into six joints or chambers, and each of these by a radial beam into a pair of chambers. The five radial beams arise from the innermost chamber of the central disk, and end in the five terminal spines. The diameter of the central disk is larger than the length of the arms. The angles between the arms are equal and filled up by an incomplete patagium, so that the whole disk forms a regular pentagon with five concave sides.
Dimensions.—Radius of each arm (without terminal spine) 0.14; breadth at their base 0.02, at their terminal joint 0.03; radius of the central disk 0.06.
Habitat.—Pacific, central area, Station 266, depth 2750 fathoms.
2. Pentinastrum goniaster, n. sp.
? Stephanastrum sp., Bury, 1862, Polycystins of Barbados, pl. xx. fig. 1.