20 DESCRIPTION OF FIFTY-TWO SPECIES OF UNIONID^. 



Proc. Acad. Nat. Sci., 1871, p. 191. 



Hab. — East Tennessee, Dr. Edgar. 



My cabinet. 

 Piam. -8, Length 1-2, Breadth 2-2 inches. 



Shell smooth, narrow elliptical, somewhat inflated, very inequilateral, round 

 before and obtusely angular behind; substance of the shell somewhat thick, thicker 

 before ; beaks rather prominent, nearly terminal ; ligament rather long and dark 

 brown ; epidermis dark olive and very much rayed on the posterior portions, with 

 rather close marks of growth ; umbonial slope slightly raised and rounded ; poste- 

 rior slope narrow elliptical ; cardinal teeth rather small, tuberculate and double in 

 both valves ; lateral teeth very long, lamellar and nearly straight ; anterior cica- 

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

 large and slightly impressed; dorsal cicatrices placed in a row across the centre of 

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

 shallow and nearly rounded; nacre purple and very iridescent. 



Remarks. — Among the shells sent to me many years since were two specimens 

 which I could not place with any I was acquainted with. These have been laid 

 aside with the hope of getting others of different ages, better to satisfy myself. 

 Since then, among all the many envois from East Tennessee, I have never seen a 

 third specimen. I am now, however, satisfied from the view of many allied spe- 

 cies, that these must be placed in the group of rutilans (nobis) as distinct, being 

 near to that and suhellipsis (nobis). It is not so large a species as rutilans, nor so 

 transverse, and differs in having a purple nacre, and in this respect differs from 

 suheUijJsis, to which it has a strong resemblance. The nacre of the two specimens 

 before me is purple in the cavity, being more intense towards the cavity of the 

 beaks, and inclining to salmon color towards the margin. It is exceedingly brilliant 

 in the posterior half of the disk. The beaks being eroded, the undulations of the 

 tips were not observable. Dr. Edgar did not mention the particular habitat of 

 those specimens, but they probably came from the Holston River. 



Unio Santeensis. pi. 6, fig. 17. 



Testa Iffivi, suboblonga, subinflata, valde infequilaterali, antice rotundata, postice obtuse biangulata; 

 valvulis crassiusculis, natibus prominulis, ad apices minute undulatis; epidermide tenebroso-fusca, 

 nitida et valde radiata; dentibus cardinalibus parvis, compressis et in utroque valvulo duplicibus; 

 lateralibus longis subcurvisque; margarita vel purpurea vel salmonis colore tincta et iridescente. 



Shell smooth, somewhat oblong, somewhat inflated, very inequilateral, rounded 

 before, obtusely biangular behind ; valves somewhat thick ; beaks sHghtly promi- 



