236 DESCRIPTION OF 



Shell elliptical, rather compressed, inequilateral, subangular behind, some- 

 what carinate on the umbonial slope; substance of the shell thin, thicker be- 

 fore; beaks somewhat prominent; ligament short and thin; epidermis yellowish 

 brown, finely striate, and with numerous marks of growth, apparently without 

 rays; cardinal teeth small, single in the right and double in the left valve; 

 lateral teeth short and straight with a direction over the cardinal tooth; anterior 

 cicatrices distinct; posterior cicatrices distinct; dorsal cicatrices placed under 

 the posterior part of the cardinal tooth; cavity of the shell small; cavity of the 

 beaks rather shallow and angular; nacre white. 



RemarTis. — A single specimen only of this shell is before me. It possesses 

 no remarkable characters, but is obviously distinct from any shell with which 

 I am acquainted. It has some resemblance on one side to V. Ravenelianus, 

 (nobis,) and on the other to cariosus, Say. The beaks being eroded, I am un- 

 able to say what kind of undulations, if any, they may have possessed. 



Unio Duttonianus. Plate 22, Fig. 50. 



Testa valdl transversa, cylindracea, valde inaquilaterali, postice angtilata; valvulis subcrassis ; nati- 

 bus vix prominentibus ; epidermide tenebroso-fusca, obsolete radiata; dentibus cardinalibus minimis; 

 lateralibus longissimis rectisque; margarita alba et iridescente. 



Shell very wide, cylindrical, very inequilateral, angular behind; substance of the shell rather thick ; beaks 

 scarcely prominent; epidermis dark brown, obsoletely radiated ; cardinal teeth very small; lateral teeth 

 verj' long and straight; nacre white and iridescent. 



Hab. Ogechee Canal, Savannah, Geo. T. R. Button. 



Cabinet of Mr. Dutton. 

 Diam. .7, Length .1, Breadth 2.8 inches. 



Shell very wide, cylindrical, very inequilateral, angular behind; posterior 

 slope wide, flattened, with two lines from the beaks to the posterior margin ; 

 substance of the shell rather thick; beaks scarcely prominent; ligament rather 

 thick and long; epidermis dark brown and very obscurely rayed; cardinal 

 teeth very small, tubercular; lateral teeth very long, thin and straight; anterior 

 cicatrices distinct; posterior cicatrices confluent; dorsal cicatrices small and 

 placed in the centre of the cavity of the beaks; cavity of the shell deep and 



