376 UNIVALVE SHELLS 



toothed, of which three are situate on the transverse 

 portion of the lip, parallel to each other, equidistant, 

 the superior and inferior ones being small, the latter 

 sometimes obsolete, the intermediate one lamelliform, 

 prominent, and the two others situate on the columel- 

 la, approximate, extending at right angles to the three 

 preceding ones, the superior one oblique and smaller: 

 labrum reflected but not flattened, bidentate, teeth 

 lamelliform, prominent ; umbilicus distinct. 



Length less than one-tenth of an inch. 



Breadth nearly one-twentieth of an inch. 



Animal. Tentacula two, rather long and thick, 

 cylindrical-obconic, retractile, with a rounded occuli- 

 ferous extremity ; foot white ; head and neck, as far 

 as the mantle, black. 



Inhabits Pennsylvania. 



Numerous specimens were discovered by Mr. 

 William Hyde in the vicinity of this city, and 1 ob- 

 tained others at Harrigate. 



The smallest teeth of the labium are sometimes 

 obsolete. 



V. *pentodon. Shell dextral, subovate, whitish 

 horn-colour; ajpex obtuse; whorls ^ve f glabrous, 

 convex ; suture not very deeply impressed ; aperture 

 semioval; labium two-toothed, of which a single 

 very prominent one is on the middle of the transverse 

 portion or true labium, and the other is remote, much 

 smaller, and placed in the basal angle of the colu- 

 mella ; labrum regularly arquated, tridentate, tooth 

 nearest the base very small and placed near the 



