1. Plagoniscus tripodiscus, n. sp. (Pl. [91], fig. 4).
Spines three-sided prismatic, thorny. Apical spine nearly straight, verticillate, with four to five verticils of three thorny branches, tapering towards the apex. Three basal spines somewhat shorter, curved, with three thorny edges.
Dimensions.—Length of the apical spine 0.2, of the basal spines 0.15.
Habitat.—Central Pacific, Station 263, surface.
2. Plagoniscus euscenium, n. sp.
Spines three-sided prismatic, thorny, with dentate edges, and three to six verticils of three short branches. Apical spine straight, with six verticils, nearly twice as long as the three curved basal spines, each of which bears three verticils; the basal verticils larger and ramified. Resembles somewhat Euscenium eucolpium, Pl. [53], fig. 12, but has no latticed shell.
Dimensions.—Length of the apical spine 0.3, of the basal spines 0.16.
Habitat.—North Pacific, Station 247, surface,
3. Plagoniscus cortinaris, n. sp.
Spines three-sided prismatic, straight, verticillate. Apical spine with twelve verticils, one and a half times as long as the three basal spines, each of which bears eight verticils of three branches. The branches are also prismatic, straight, on each edge parallel, tapering towards the apex, in the three basal spines forked, in the apical spine more branched. Similar to the cortinar skeleton of Clathrocorys (Pl. [64], figs. 8-10).