27 



upper half, cylindrical in the lower half, wide and blunt anteriorly, 

 with a broad very deep constriction about the middle of the last whorl ; 

 dingy white ; with very distant lamelliform transverse ribs, about ten 

 on each whorl, with strong irregular intervening strife ; spire with con- 

 vex outlines ; apex small ; whorls nine, very convex, with a deeply 

 impressed, and near the apex a chanelled, suture ; last whorl small and 

 very short ; aperture ovate, acute above, much modified by the con- 

 striction of the last whorl, which constriction bends the sharp labrum 

 into two large arcs of small circles ; columella remarkably twisted 

 and arcuate. 



Length .16 inch ; breadth .05 inch; length of aperture .033 inch. 



This species approaches Cylindrella in general form, ( so as to ren- 

 der useless the character of divergence, ) and resembles G, costulata in 

 sculpture. 



BuLnius. The first two or three following species with some de- 

 scribed above belong to a group of small shells, which are intermedi- 

 ate between Bulimus and Achatina. Those which approximate most 

 to Achatina have been referred to that genus, and the following two 

 or three conform more to the type of Bulimus. Among these shells, 

 the distinction between these two genera loses its value. 



Mr. Reeve has described a species of this group, of which some in- 

 dividuals have, and some have not a truncated columella. 



Bulimus kitidiusculus. Shell long ovate conic ; dingy white ; 

 smooth and shining, with a few very distant excessively minute trans- 

 verse strise ; spire with nearly rectilinear outlines ; apex rather ob- 

 tuse ; whorls nearly six, rather convex, with a well impressed suture 

 last whorl long ; aperture long ovate, quite acute above ; labrum very- 

 thin and sharp ; columella somewhat twisted. 



Mean divergence 24° ; length .24 inch ; breadth .1 inch ; length of 

 aperture .1 inch. 



Bulimus pauperculus. Shell much elongated, rcgula?-ly taper- 

 ing to the summit ; Avhite, with a thin horn colored epidermis ; with 

 numerous broad lightly impressed arcuate transverse strife ; spire with 

 rectilinear outlines ; apex rather obtuse ; whoi'ls seven, rather convex, 

 with a well impressed suture ; aperture long ovate, quite acute above ; 

 labrum thin and sliarp ; columella well thickened. 



Mean divergence 18°; length .25 inch; breadth .25 inch; length 

 of aperture .075 inch. 



