50 DESCRIPTION OF FIFTY-TWO SPECIES OF TNIONID^. 



The well defined transverse bands of the marks of growth are more developed 

 than usual, and the obscure capillary rays over the whole disk are unusual. The 

 nacre is generally of a fine salmon color, sometimes it is white. None of the 

 specimens before me are purplish, nor were they perfect enough to display the 

 character of the tips of the beaks. This species belongs to the group of which 

 Abhevillensis may be considered the type. That species has not the smooth polished 

 epidermis which ligatus has. 



Unio bellulus. pi. 17, fig. 48. 



Testa Isevi, obliqua, tumida, ad latere parum planulata, valde insequilaterali, postice obtuse angular!, 

 antice oblique rotundata ; valvulis percrassis, antice crassioribus ; natibus pyramidatis, fere ter- 

 minalibus ; epidermide luteola, valde radiata ; dentibus cardinalibus subcrassis, rugosis ; lateral- 

 ibus Curtis, crassis rugosisque ; margarita argentea et valde iridescente. 



Shell smooth, oblique, tumid, somewhat flattened at the side, very inequilateral, 

 obtusely angular behind, obliquely rounded before; valves very thick, thicker 

 before; beaks pyramidal, nearly terminal; epidermis yellowish, very much rayed; 

 cardinal teeth rather thick and rugose ; lateral teeth short, thick and rugose ; 

 nacre silver white and very iridescent. 



Proe. Acad. Nat. Sci., 1872, p. 161. 



Hah. — Holston River, Dr. Edgar; Tennessee River, Rev. G. White; Mussel 

 Shoals, Tennessee River, Alabama, C. M. Wheatley. 



My cabinet and cabinet of C. M. Wheatley. 

 Diam. -9, Length 1-2, Breadth 1*3 inch. 



Shell smooth, oblique, tumid, somewhat flattened at the sides, very inequilateral, 

 obtusely angular behind, obliquely rounded before ; substance of the shell very 

 thick, thicker before ; beaks pyramidal, nearly terminal ; ligament short and light 

 brown ; epidermis yellowish, with broad interrupted green rays and somewhat dis- 

 tant marks of growth ; umbonial slope rounded ; posterior slope cordate, yellow, 

 with two dotted rays from the beak to posterior margin in each valve ; cardinal 

 teeth rather thick and rugose ; lateral teeth short, thick, rugose and very oblique ; 

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

 and well impressed; dorsal cicatrices placed nearly over the centre of the cavity of 

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

 and obtusely angular ; nacre silver white and very iridescent. 



Remarks. — Several specimens of different ages are before me. Some of middle 

 age I have had for many years. The adult from Mr. Wheatley, recently received, 

 satisfied me that the species was undescribed. The beautiful broad green inter- 



