Shell hemispherical, with small irregular roundish pores. Basal lattice with four large meshes, two major cardinal and two minor jugular pores. Apical horn and the three feet of similar form and size, slender prismatic, straight, twice to four times as long as the shell. Three lateral wings nearly semicircular, densely latticed, with the same pores as the shell, and smooth convex margin. _Dimensions._--Shell 0.05 long, 0.06 broad. _Habitat._--South Pacific, Station 295, depth 1500 fathoms. 5. _Archiscenium callimitra_, n. sp. Shell campanulate, with irregular polygonal pores. Basal lattice with nine meshes (three larger central and six smaller distal pores, as in _Callimitra carolotæ_, Pl. 63, fig. 8). Apical horn straight, prismatic, slender, conical, twice as long as the shell. Feet longer and more slender, slightly curved. Three lateral wings very broad, densely fenestrated, with irregular polygonal pores of the same shape as in the similar _Callimitra carolotæ_ (Pl. 63, fig. 1). _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. {1152}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.