195 



areturreted; the aperture entire, oval, and oblong; the 

 columella callous at the upper part, truncated at the 

 base; the right side of the margin separated by a sinus 

 or notch. Shell with an operculum. 



Melanopsis costata Melanopsis laevigata. 



PIRENA. 



Enci/cl. Meth. pi 458, /. 2, A. B. 



The G. Pirena resembles the G. Melania and G. Me- 

 lanopsis, but more particularly the former genus : from 

 the latter however, it is principally distinguished by 

 not having any particular callosity; and it cannot be 

 confounded with the G. Melania, the right margin 

 having a sinus at the base, and another at the summit; 

 consequently the shells of this genus present two 

 notches, while those of the G. Melanopsis and G. Me- 

 lania exhibit only one. It is a turreted shell, the 

 aperture oblong, right lip sharp, and the base of the 

 columella inclined towards the right side. The oper- 

 culum is horny. 



Pirena terebralis Pirena aurita 

 spinosa granulosa. 



o2 



