42 DESCRIPTION OF FIFTY-TWO SPECIES OF UNIONID^. 



Unio differtus. pi. 14, fig. 39. 



Testa Isevi, suboblonga, ventricosa, subsequilaterali, postice obtuse biangulari, fere rotunda, antice 

 rotundata ; valvulis crassis, antice crassioribus ; natibus vix prominulis ; epidermide subpolita, 

 luteola et obsolete radiata; dentibus cardinalibus parviusculis, corrugatis, compressis et in utroque 

 valvulo duplicibus ; lateralibus longis, lamellatis subrectisque ; margarita vel albida vel salmonis 

 colore tincta et valde iridescente. 



Shell smooth, suboblong, ventricose, subequilateral, obtusely biangular behind, 

 almost round, rounded before; valves thick, thicker before; beaks scarcely promi- 

 nent; epidermis somewhat polished, yellowish and obscurely radiated; cardinal 

 teeth rather small, corrugate, compressed and double in both valves ; lateral teeth 

 long, lamellar and nearly straight; nacre salmon colored or white and very iridescent. 

 Proc. Acad. Nat. Sci., 1812, p. 158. 



Hab. — Georgia] Major J, Le Conte. 



My cabinet and cabinet of the Academy Natural Sciences. 

 Diam. 1-3, Length 1-7, Breadth 3-2 inches. 



Shell smooth, elliptical, ventricose, subequilateral, obtusely biangular behind, 

 almost round, rounded before ; substance of the shell thick, thicker before ; beaks 

 scarcely prominent; ligament rather short and thick; epidermis somewhat polished, 

 yellowish and obscurely radiated; umbonial slope rounded ; posterior slope widely 

 elliptical, subcarinate, with several impressed lines from the beaks to the margin ; 

 cardinal teeth rather small, corrugate, compressed and double in both valves ; late- 

 ral teeth long, lamellar, nearly straight and enlarged at the posterior end; anterior 

 cicatrices distinct, large and well impressed; posterior cicatrices confluent, large 

 and moderately impressed ; dorsal cicatrices placed in the centre of the cavity of 

 the beaks; cavity of the shell deep and wide; cavity of the beaks shallow and 

 rounded ; nacre light salmon colored or white and very iridescent. 



Remarks. — Two specimens are before me. That which is figured is more inflated 

 than the other and is probably a female. They came from the late Major Le 

 Conte's collection, and although no habitat was attached to them, I have no doubt 

 that they came from Georgia, as many of the new species given to me by him were 

 from Liberty County of that State. The lines of growth are very distant. There 

 are two specimens before me and these are moderately large and no doubt full 

 grown. In outline differtus is near to Savannahensis (nobis), but difl"ers in not 

 having the side flattened and having a rounded umbonial slope. It is also near to 

 Cuvierianus (nobis), but is not quite so oblique. One of the specimens, although 

 eroded, shows imperfect undulations of the tips. 



