1. Arachnocalpis ellipsoides, n. sp. (Pl. [98], fig. 13).
Shell ellipsoidal, one and a half times as long as broad, on the apical pole hemispherical, on the basal pole coronate, with an elegant prominent funnel-shaped peristome, which is one-eighth as broad as the shell, fenestrated by very fine pores, and bears fifteen to twenty short conical divergent teeth. Inner shell with irregular polygonal meshes of very different size, separated by thin, finely-denticulate bars. Outer spongy shell very delicate, arachnoidal, with numerous prominent conical spongy papillæ. Central capsule ellipsoidal, half as long and broad as the shell.
Dimensions.—Shell 0.46 long, 0.32 broad; mouth 0.045 broad.
Habitat.—Central Pacific, Stations 271 to 274, surface.
2. Arachnocalpis sphæroides, n. sp.
Shell spheroidal, of the same structure as the preceding ellipsoidal species, with the same form of the spongy envelope; differing from it in the globose form and the shorter peristome, bearing only nine or ten small conical divergent teeth. Central capsule spherical.
Dimensions.—Shell 0.3 diameter, mouth 0.04 broad.
Habitat.—Central Pacific, Stations 265 to 270, surface.
Subfamily 2. Archiphænida, Haeckel, 1881, Prodromus, p. 429.
Definition.—Phænocalpida with the basal mouth of the shell fenestrated (vel Monocyrtida multiradiata clausa).