156 UNIVALVE SHELLS 



Transverse diameter more than 3-10. 



Height of the columella above 3-20. 



Inhabits Lower Missouri. 



Of two specimens which I obtained, the larger one 

 had six volutions, and the smaller one had eight; the 

 superior tooth in the larger was concave towards the 

 base of the shell. It is a remarkable and very dis- 

 tinct species. 



9. H. *chersina. Shell subglobose- conic, pale 

 yellowish-white, pellucid, convex beneath; volutions 

 about six, wrinkles not distinct ; spine convex- ele- 

 vated ; suture moderate ; body whorl slightly cari- 

 nated on the middle; mouth nearly transverse, un- 

 armed, the two extremities nearly equal; labrum 

 simple; umbilicus none. 



Inhabits the Sea Islands of Georgia. 



Breadth 1-10 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. laby- 

 rinthica. 



10. H. *gularis. Shell subglobose, pale yel- 

 lowish-horn colour, 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; la- 

 brum not reflected; throat far within upon the side of 

 the labrum bidentate, teeth lamelliform, of which one 



