28 DESCRIPTION OP FIFTY-TWO SPECIES OF UNIONIDJE. 



Diam. -7, Length 1, Breadth 1-2 inch. 



Shell smooth, triangular, compressed, flattened at the sides, very inequilateral, 

 rounded before and subbiangular behind ; substance of the shell rather thick, thicker 

 before; beaks prominent, almost terminal; ligament short and light brown; epi- 

 dermis yellowish, with a few interrupted maculate rays near the umbonial slope, 

 with close marks of growth; umbonial slope obtusely angular; posterior slope com- 

 pressed cordate; cardinal teeth rather thick, somewhat compressed and crenulate ; 

 lateral teeth rather thick, short and nearly straight ; anterior cicatrices distinct, 

 small and deeply impressed ; posterior cicatrices distinct, small and well impressed ; 

 dorsal cicatrices placed on the under side of the plate, within the cavity of the beaks ; 

 cavity of the shell very shallow; cavity of the beaks shallow and obtusely angular; 

 nacre white and very iridescent. 



Remarks. — Three specimens are before me, all found by Miss Law in the Holston 

 Eiver and sent to Dr. Lewis, to whom I am obliged for the advantage of describing 

 the species and having one of them in my cabinet. In outline this species is near to 

 CUnchensis (nobis), but may be distinguished at once by its flattened sides and more 

 terminal beaks. In the marks of growth they differ much, acuens having them 

 much closer. In regard to the interrupted green rays they are very similar, but in 

 CUnchensis these are more numerous and spread more over the disk. This species 

 is also closely allied to mundus (nobis), but it is more compressed and less oblique. 

 The only three specimens I have seen are nearly of the same size and are, I presume, 

 adults. The beaks are too much eroded to present the character of undulations. 

 Each of the specimens presents about a dozen marks of growth. 



Unio flavidus. pi. 9, fig. 25. 



Testa Isevi, triangulari, subinflata, ad latere plfinulata, insequilaterali, postice obtuse angulata, antice 

 rotundata; valvulis subcrassis, antice crassioribus ; natibus prominentibus, recarvatis, ad apices 

 minute undulatis ; epidermide flavida, radiis interruptis; dentibus cardinalibus parvis corruga- 

 tisque; lateralibus curtis, subcrassis subcurvisque; margarita argentea et iridescente. 



Shell smooth, triangular, somewhat inflated, flattened at the sides, obtusely 

 angular behind and rounded before ; valves somewhat thick, thicker before ; beaks 

 somewhat prominent, incurved, minutely undulate at the tips; epidermis yellowish, 

 with interrupted rays; cardinal teeth small and corrugate; lateral teeth short, rather 

 thick and somewhat curved ; nacre silver white and iridescent. 

 Proc. Acad. Nat. Sci., 18t2, p. 156. 



Hah. — Clinch Hiver, Anderson Co., and Holston Eiver, East Tenn., Miss A. E. 

 Law ; North Alabama, Kev. G. White. 



