1172 THE VOYAGE OF H.M.S. CHALLENGER. 



5. Carpocanistrum evacuatum, n. sp. (PL 52, fig. 11). 



Shell urceolate, smooth, thin-walled, one and a half times as long as broad. Pores regular 

 circular, sixteen to twenty on the greatest breadth of the shell. Peristome slightly constricted, 

 with twenty to twenty-five small triangular vertical feet. 



Dimensions. Shell 01 long, 0'07 broad ; mouth 0'05 broad. 



Habitat. Central Pacific, Station 272, depth 2600 fathoms. 



6. Carpocanistrum pyriforme, Haeckel. 



Lithocarpium pyriforme, Stohr, 1880, Palseontogr., 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 017 long, 014 broad ; mouth 0'035 broad. 



Habitat. Fossil in Tertiary rocks of Sicily (Grotte) Stohr. 



Genus 521. Arachnocalpis, 1 Haeckel, 1881, Prodromus, p. 427. 



Definition. A rchiphormida (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. 



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- 



1 Arachnocalpis = Urn enveloped by spider's web; 



