Habitat.—Central Pacific, Station 274, surface.
2. Phractacantha bipennis, n. sp.
Spines compressed, two-edged, tapering from the broader middle towards the two ends. Apex simple. Base pyramidal, without leaf-cross. From the middle arise two opposite broad, forked apophyses; ends of the fork-branches broad and obtuse.
Dimensions.—Length of the spines 0.15, breadth in the middle 0.012.
Habitat.—Central Pacific, Station 266, surface.
Genus 328. Doracantha,[[368]] Haeckel, 1881, Prodromus, p. 465.
Definition.—Astrolonchida with two latticed or fenestrated apophyses on each radial spine.
The genus Doracantha arises from the foregoing Phractacantha by union of the fork-branches of the apophyses on each spine. By this concrescence is formed a polygonal or roundish plate with two pores, pierced by the radial spine between them. Doracantha may be regarded as a Dorataspis, in which the twenty small fenestrated plates have not become united.
1. Doracantha dorataspis, n. sp.
Spines compressed, two-edged, tapering from the broader middle towards the two ends. Apex simple. Base pyramidal, without leaf-cross. From the middle part of each spine arise two opposite forked apophyses; the neighbouring fork-branches are recurved and united in the tangential plane; so that each spine bears a plate or shield with two elliptical pores; the margin of the roundish plate bears a variable number of short teeth.