NERITID^. 293 



developed, usuall}- soldered by its extreme edge to the last 

 whorl, and forming over the umbilicus an arch, having the 

 opening larger than the aperture of the shell. S. Philippiana, 

 C. B. Ad. (Ixxvii, 45, 46). 



Proserpina, Guilding. 



Syn. — Odoutostoma, d'Orb. 



Distr. — *7 sp. West Indies, Northern So. America. P. dept^essa, 

 d'Orb. (Ixxvii, 47). 



Shell orbicular-depressed, polished, covered at the base by a 

 shining callus ; aperture semioval, lip sharp ; columella and 

 parietal wall with dentiform lamellae, No operculum. 



PROSERPiNELLA, Bland, 1865. Columellar fold absent ; having a 

 single parietal tooth. P. Berendti, Bid. Mexico. 



CYANE, H. Ad., 1870. Columella truncate below. P. Blandiana, 

 Ad. Peru. 



Ceres, Gray. 



Distr. — 2 sp. Mexico. C. eolina, Duclos (Ixxvii, 49). Shell 

 heliciniform, carinated at the periphery, upper surface rugose, 

 epidermis thin, callous at the base ; lip sharp, with spiral laminae 

 within the aperture ; columella with dentiform laminae. 



Order SCUTIBRANCHIATA. 5t>t. Ut h,i^Ci- 



Branchiae pectinated, placed in a cavity in the upper part of 

 the neck, or at the inferior edge of the mantle, around the foot. 

 Dioecious. 



Shell usually spiral (globular or pyramidal) or conical, holos- 

 tomate. 



Suborder podopthalma. Shell spiral. Operculum usually 

 present and paucispiral or multispiral. Eyes on peduncles, 

 separate from the tentacles. 



Suborder edriopthalma. Shell conical, not spiral ; no oper- 

 culum ; eyes sessile. 



Suborder PODOPTHALMA. 

 Family NBRITID^. 



Shell thick, semiglobose, porcellanous ; spire ver}^ small ; cavity 

 simple, from the absorption of the internal portions of the whorls ; 

 aperture semilunate ; columellar side expanded and flattened ; 

 outer lip acute. Operculum shelly, subspiral, articulated. 



At each end of the columella there is an oblong muscular 

 impression, connected on the outer side by a ridge, on which 

 the operculum rests ; within this ridge the inner layers of the 

 shell are absorbed. 



Animal with a broad, short muzzle, and long slender tentacles ; 

 eyes on prominent pedicels, at the outer bases of the tentacles ; 



