18 



essentially by the much more elevated spire, and by the superior 

 half of the dilated lip being abruptly narrowed so as to form a 

 prominent angle near the middle. It is also a much thicker shell. 

 H. INTERNA. — Shell yellowish red ; volutions six or eight ; 

 whorls with regular, equidistant, elevated, obtuse lines across 

 them, separated by regular grooves ; lines obsolete beneath ; spire 

 convex, little elevated ; aperture very straight, transverse, less 

 than one half of the longitudinal diameter ; labrum not reflected ; 

 within, upon the side of the labrum, two prominent, lamelliform 

 teeth, of which the superior one is largest, and neither of them 

 attain the edge of the lip ; region of the base of the columella 

 much indented ; umbilicus obsolete or wanting. 



Transverse diameter more than three-tenths. Height of the 

 columella about three-twentieths of an inch. Inhabits Lower Mis- 

 souri. 



Of two specimens which I obtained, the larger one had six 

 volutions, and the smaller one had eight ; the superior tooth in the 

 larger one was concave towards the base of the shell. It is a 

 remarkable and very distinct species. 



H. CHERSINA — Shell subglobose- conic, pale yellowish white, 

 pellucid, convex beneath ; volutions about six, wrinkles not dis- 

 tinct ; spire convex-elevated ; suture moderate ; body whorl 

 slightly carinated on the middle ;. mouth nearly transverse, un- 

 armed, the two extremities nearly equal ; labrum simple : umbilicus 

 none. 



Inhabits the Sea Islands of Georgia. Breadth one-tenth of an 

 inch. Cabinet of the Academy. 



A very small species. But one specimen occurred in a cotton 

 field. It is rather larger than H. labyrinthica. 



H. GUi.ARis. — Shell subglobose, pale yellowish horn color ; 

 polished, pellucid, beneath near the aperture whitish-yellow opake; 

 volutions six or seven, with prominent, somewhat regular wrinkles ; 

 spire convex, a little elevated ; suture moderate ; labrum not re- 

 flected ; throat far within upon the side of the labrum, bidentate ; 

 teeth lamelliform, of which one is oblique and placed near the 

 middle, and the other less elongated, placed near the base ; um- 

 bilicus none. 



lireadth more than one-fourth of an inch. Inhabits Ohio and 

 Pennsylvania. 



