Dimensions.—Shell 0.1 long, 0.07 broad; mouth 0.05 broad.
Habitat.—Central Pacific, Station 272, depth 2600 fathoms.
6. Carpocanistrum pyriforme, Haeckel.
Lithocarpium pyriforme, Stöhr, 1880, Palæontogr., vol. xxvi. p. 97, Taf. iii. fig. 10.
Shell pear-shaped or subspherical, one and a fourth times as long as broad. Pores roundish, polygonally framed (or with square meshes ?). Peristome strongly constricted, one-fourth as broad as the shell, somewhat tubular, with twelve to twenty short vertical and parallel feet. The position of this species is doubtful; perhaps it represents a peculiar genus.
Dimensions.—Shell 0.17 long, 0.14 broad; mouth 0.035 broad.
Habitat.—Fossil in Tertiary rocks of Sicily (Grotte) Stöhr.
Genus 521. Arachnocalpis,[[138]] Haeckel, 1881, Prodromus, p. 427.
Definition.—Archiphormida (vel Monocyrtida multiradiata aperta) with an ellipsoidal or nearly spherical double shell; outer shell arachnoidal or spongy. Peristome small, constricted with a corona of numerous radial feet. No apical horn.
The genus Arachnocalpis differs from the other Archiphormida by possessing a double shell (like Peripyramis). The large shell, reaching nearly half a millimeter in length is either ellipsoidal or nearly spherical, and composed of an inner primary and an outer secondary shell. Its network is very delicate, in the outer envelope either spongy or arachnoidal. This very remarkable genus has probably no true relation to the other Archiphormida but has been derived from true Calpoidea (Mitrocalpis) by development of a corona around the mouth.