OP CONCnOLOGY. 167 



Mesembrinus, Albers. Ovate-conical, rimate, rather thin, 

 striate, white, generally variegated with brown ; aperture 

 oblong-oval, small, lip thin, and not reflected, columellar 

 margin more or less dilated, reflected and appressed, colu- 

 mella slightly twisted. 



Thaumastus, Albers. Shell oblong-conical, imperforate 

 or rimate, nearly smooth, white, sometimes variegated with 

 brown flames; aperture oblong-oval, lip obtuse, straight or 

 slightly expanded, columellar margin reflexed, more or less 

 appressed, columella distinctly twisted. 



MoRMUS, Albers. Shell oblong- conical, striate or subcos- 

 tate, thin, whitish or variegated with brown, upper whorls 

 flattened, the body whorl very convex, inflated ; aperture 

 subovate, the lips simple, sharp, columellar margin dilated 

 and reflected. 



ScuTALUS, Albers. Ovate-conical, perforate or umbilicate, 

 roughly striate, whitish or brownish Avhite, seldom varie- 

 gated, last whorl ventricose, compressed at the base ; 

 aperture ovate-oblong, peristome more or less expanded, 

 slightly thickened within. 



Peron^US, Albers. Oblong-turrited, perforate, white, some- 

 times variegated with brownish, spire elevated, the last 

 whorl one-third of the total length ; aperture oblong-oval, 

 lip expanded, not thickened, columellar margin dilated ; 

 columella receding or obsoletely arcuate. 



DRYMiEUS, Albers. 

 1. Drymseus serperastrus, Say. 



Plate 13, figure 4. 



Shell ovate-fusiform, nmbilicate, thin, translucent ; spire 

 acuminata, suture moderately impressed ; whorls about 7, a 

 little convex ; aperture elongate-lunate, the lip expanded a 

 little, and reflected upon its columellar margin ; umbilicus 

 moderate. Yellowish white, with about six interrupted bluish 

 black bands on the body Avhorl, which sometimes coalesce ; the 

 internal coloring is the same, except near the lip margin, where 

 the bands disappear. 



Length 37, diam. 17*5 mill. 



Texas and Mexico. 



