*• 



162 UNIVALVE SHELLS 



acute angle at the centre of the aperture; beneath, ex- 

 hibiting only two volutions, of which the external one 

 is slightly grooved near the suture. 



Breadth 1-4 of an inch. 



Inhabits Alabama. 



Cabinet of the Academy. 



This species is about the same size with P. avara, 

 but, besides other characters, it is sufficiently dis- 

 tinguished by the acute fold of the labrum. It was 

 sent to the Academy by Mr. Samuel Hazard. 



Genus Pupa. 



1. P. *armifera. Shell dextral ; oblong-oval or 

 somewhat obtusely fiisiform ; suture distinct ; whirls 

 six, obsoletely wrinkled; aperture longitudinally 

 subovate ; exterior lip reflected, but not flattened, in- 

 terrupted aboxe by the penultimate whirl, and with 

 five teeth, of which the superior one, and that which 

 precedes the basal one, are smallest ; labrum with 

 an undulated lamelliform tooth, its anterior extremity 

 little elevated, but elongated, so as almost to join the 

 superior extremity of the exterior lip. 



Length, 3-20 of an inch. 



Inhabits Upper Missouri. 



Var. a. The two smaller teeth obsolete or want- 

 ing. 



Var. b. The basal tooth obsolete or wanting. 



Very distinct from corticaria in being a much 

 larger and proportionally more dilated shell,and with 

 that species, and the next^ seems to belong more pro- 



