1186 THE VOYAGE OF H.M.S. CHALLENGER. 



the preceding genus Archicorys, from which it differs in the total absence of an apical 

 horn. There is no trace of any triradial structure, excepting in some smaller species, in 

 which the basal part of the central capsule is trilobate ; these may be derived from the 

 Dicyrtides Sethocorys or Dictyocephalus, by loss of the cephalis and the cortinar 

 septum. But the larger species, which have a quite simple, ovate, central capsule 

 (PI. 51, fig. 13), have probably an independent origin, from Cystidium. 



1. Cyrtocalpis urceolus, n. sp. (PI. 51, fig. 13). 



Shell smooth, urceolate, with very delicate and elegant network. Pores in the middle part 

 large, regular, hexagonal, towards each pole smaller, irregular, roundish or polygonal. Mouth with 

 broad, hyaline, annular peristome, about one-third as broad as the shell. 



Dimensions. Shell 016 long, 012 broad ; mouth 0'05 broad. 



Habitat. Mediterranean (Portofino near Genoa), surface. 



2. Cyrtocalpis reticulum, n. sp. 



Shell smooth, urceolate, very similar to the preceding species, but differing from it in the 

 densely reticulated framework of the shell, which is composed of very numerous and small, irregular, 

 polygonal meshes of nearly equal size. Mouth without peristome, half as broad as the shell. 



Dimensions. Shell 018 long, 015 broad ; mouth 0'07 broad. 



Habitat. Tropical Atlantic, Station 347, depth 2250 fathoms. 



3. Cyrtocalpis amphora, Haeckel. 



Cyrtocalpis amphora, Haeckel, 1862, Monogr. d. Radio!., p. 286, Taf. v. iig. 2. 



Shell smooth, urceolate, with regular, circular pores of equal size, of about the same breadth a.s 

 the bars. Mouth with smooth peristome, about half as broad as the shell. 

 Dimensions. Shell 012 long, 0'08 broad ; mouth 0'04 broad. 

 Habitat. Cosmopolitan ; Mediterranean, Atlantic, Pacific ; surface, and at various depths. 



4. Cyrtocalpis urna, Stohr. 



Cyrtocalpis urna, Stohr, 1880, Palseontogr., vol. xxvi. p. 96, Taf. iii. fig. 7. 



Shell smooth, urceolate, with subregular, circular pores of different sizes, gradually increasing 

 towards the mouth, of about the same breadth as the bars. Mouth without peristome (?), about 

 half as broad as the shell. 



Dimensions. Shell 0'09 long, 0'06 broad ; mouth 0'035 broad. 



Habitat. Fossil in tertiary rocks of Sicily (Grotte). 



