Dimensions.—Shell 0.05 long, 0.04 broad.
Habitat.—Western Tropical Pacific, Station 225, depth 4475 fathoms.
Genus 507. Pteroscenium,[[124]] Haeckel, 1881, Prodromus, p. 429.
Definition.—Archiperida (vel Monocyrtida triradiata clausa) with a free branched internal columella, prolonged into an apical horn. Three basal feet connected with the horn by three vertical lateral wings.
The genus Pteroscenium differs from the preceding Archiscenium only in the ramification of the internal columella, and therefore exhibits to it the same relation that Cladoscenium bears to Euscenium. The branches of the columella form also here verticils of ascending branches, three in each verticil, and their distal ends are inserted on the inner surface of the lattice-shell.
1. Pteroscenium arcuatum, n. sp. (Pl. [98], fig. 4).
Shell campanulate, smooth, nearly conical, somewhat broader than long, with irregular dense network of small circular pores. Columella straight, with two or three triradiate verticils of horizontal lateral branches, which are inserted in the shell-wall. Horn slender pyramidal, as long as the shell. Three divergent feet twice as long as the horn, strongly curved, thorny, three-edged; the distance of their pointed ends twice as broad as the shell. From the outer edge of each foot arise numerous ascending bristles, which are connected together and with similar lateral branches of the horn by curved arches, forming three delicate spiny vertical wings.
Dimensions.—Shell 0.06 long, 0.08 broad.
Habitat.—Central Pacific, Station 271, depth 2425 fathoms.
2. Pteroscenium arcadophorum, n. sp.