178 UNIVALVE SHELLS 



it is probable its station will be between the genera 

 Melania and Acathina. I propose for it the generic 

 name of ANCULOSA. 



5. M. *armigera. Shell tapering, brownish-horn 

 colour ; volutions about six, slightly wrinkled ; spire 

 near the apex eroded, whitish ; body whirl with a 

 revolving series of about five or six distant, promi- 

 nent tubercles, which become obsolete on the spire, 

 and are concealed by the revolution of the succeeding 

 whirls, in consequence of which arrangement there 

 is the appearance of a second, smaller, and more ob- 

 tuse subsutural series of tubercles on the body whirl ; 

 two or three obsolete revolving reddish-brown lines ; 

 aperture bluish- white within 5 a distinct sinus at the 

 base of tne columella. 



Inhabits Ohio Uiver. 



Length about one inch. 



Distinguished from other N. American species, by 

 the armature of tubercles. 



GENUS BULLA. 



13. fluviatilis. Shell sub-oval, pellucid, pale yel- 

 lowish white, finely wrinkled ; volutions three ; body 

 whirl large with a prominently carinated shoulder 

 bounding the spire ; spire perfectly flat or slightly 

 concave, giving to the shell a perfectly truncated ap- 

 pearance in that part ; aperture longer than the co- 

 lumella, oblong-ovate, extending beyond the tip of 

 the spire ; umbilicus profound, edged by a slight 

 carina. 



