prominently and almost acutely vaulted above ; its basal 

 portion not extending below the level of the base ; some- 

 times expanded ; animal ferruginous, with numerous yel- 

 lowish dots ; tentacula dotted and flexuous. 



SYNONYMS. 



p. BicARiNATus, S., Amev. Ed. af Nicholson's Encycl.f 



Article Conchology, pi. 1, fig. 4. 

 Helix angulatus, Backet, Linn. Trans, vol. 13, p. 42, 



pi. 5, fig. 1. 

 P. BICARINATUS, Sowcrby's Genera. 



OBSERVATIONS. 



It has some resemblance to the trivolvis, but differs in 

 the remarkably umbilicated form of the spire; it is also 

 irregularly wrinkled, and is furnished with minute strix, 

 never visible in that species; the superior portion of the 

 labrum is more prominently vaulted, and the carinas are 

 more conspicuous. It is an inhabitant of the same exten- 

 sive region as the trivolvis, and was obtained from Lake 

 Huron by Mr. Racket, whose name had been previously 

 applied in this genus by Brard. in the Ann. du Museum, 

 vol. 14. 



It is remarkable that Sowerby has represented this spe- 

 cies under the name of bicarinatus, apparently without be- 

 ing aware that I had previously described it under the 

 same name. 



REFERENCE TO THE PLATE. 



Fig. 3, Two views ; natural bIzo. 

 PI. 54. 



