_Dimensions._--Shell 0.07 long, 0.08 broad; horn and feet 0.16 to 0.22 long. _Habitat._--South Atlantic, Station 332, depth 2200 fathoms. Genus 506. _Archiscenium_,[123] Haeckel, 1881, Prodromus, p. 429. _Definition._--#Archiperida# (vel Monocyrtida triradiata clausa) with a free simple internal columella, prolonged into an apical horn. Three basal feet connected with the horn by three vertical lateral wings. The genus _Archiscenium_ and the following nearly allied _Pteroscenium_ are derived from the two preceding genera, from which they differ in the development of three free vertical lateral lattice-wings; these arise from the upper edge of the three basal feet and connect them with the three edges of the apical horn. The basal part of the latter, enclosed in the shell, forms an internal free columella, which in _Archiscenium_ is simple, not branched. 1. _Archiscenium quadrispinum_, n. sp. (Pl. 53, fig. 11). Shell hemispherical, smooth, with a small number of large irregular polygonal meshes and thin bars. Basal lattice with three very large central meshes and six smaller peripheral meshes (two on the base of each foot). Apical horn and the three feet of equal size and similar form, slender, pyramidal, widely divergent, straight, as long as the shell-diameter. Three lateral wings small, little prominent, each with two or three irregular meshes. Central capsule subspherical. _Dimensions._--Shell 0.05 long, 0.1 broad. _Habitat._--Central Pacific, Station 274, depth 2750 fathoms. 2. _Archiscenium clathrocorys_, n. sp. Shell campanulate, smooth, with numerous irregular square meshes. Basal lattice with three very large meshes. Apical horn and the three feet of equal size and similar form, three-sided prismatic, {1151}widely divergent, straight, twice as long as the shell-diameter. Three lateral wings broad, each with a basal row of few very large irregular roundish meshes, and several distal rows of small square meshes. This species is very similar to _Clathrocorys murrayi_ (Pl. 64, fig. 8), but has no trace of thorax-wall. The latter species may be derived from the former by development of the thoracic lattice, which connects the three free feet. _Dimensions._--Shell 0.05 long, 0.06 broad. _Habitat._--Central Pacific, Station 266, depth 2750 fathoms. 3. _Archiscenium tripterygium_, n. sp. Shell hemispherical, smooth, with numerous irregular roundish meshes of very different sizes. Basal lattice with four large meshes, two major cardinal and two minor cardinal pores. Apical horn and the three feet of similar form and size, slender prismatic, three to four times as long as the shell; the horn straight, the feet curved. Three lateral wings very delicate, with a basal row of few large irregular polygonal meshes, and several distal rows of similar small pores. _Dimensions._--Shell 0.04 long, 0.05 broad. _Habitat._--North Pacific, Station 244, depth 2900 fathoms. 4. _Archiscenium cyclopterum_, n. sp. (Pl. 98, fig. 3).