257 



Purpura hystrix 



deltoidea 



unifascialis 



retusa 



trochlea 



Purpura clavus 



fasciolaris 



vexillum 



bizonalis 



nucleus. 



MONOCEROS. 



BUCCINUM MONODON. LiniKBUS. 



Sowerbtfs Genera, No. 5, pi. 5. 



Lamarck would not have divided this genus from 

 that of Purpura, which it in every respect resembles, 

 except on account of the singular, thin, conical, some- 

 what curved tooth at the base of the right side, which, 

 being constant in many different species, renders it ex- 

 pedient to constitute a separate genus of them ; a refer- 

 ence, therefore, to the generic description of the G. 

 Purpura will suffice for this genus. It may, however, 

 be added, that the spire is more elevated in some spe- 

 cies of the G. Monoceros than in others; the exterior 

 surface of the whorls carinated and angular, smooth, or 

 with small imbricated scales in transverse rows; aper- 

 ture internally grooved; and in some species, recently 

 brought from the South Seas, the right side of the 

 opening near its edge presents one or more rows of 



