DESCRIPTION OF FIFTY-TWO SPECIES OF UNIONID.E. 13 



Hald. It differs in being rather less appressed, rather more rounded in outline, 

 and in having interrupted rays. It reminds one of dolabelloides (nobis), but it is 

 more triangular. None of the specimens are perfect enough at the beaks to dis- 

 play undulations, 



Unio radiosus. pi. 3, fig. 9. 



Testa Isevi, subtriangnlari, subinflata, subequilaterali, antice rotundata, postice obtuse angulari ; val- 

 vulis crassiusculis, antice paruin crassioribus ; natibus prominentibus ; epidermide luteo-oliva, 

 peiTadiata ; dentibus cardinalibus parvis, compressis crenulatisque ; lateralibus subcrassis, lamel- 

 latis subrectisque ; margarita alba et iridescente. 



Shell smooth, subtriangular, somewhat inflated, subequilateral, rounded before, 

 obtusely angular behind ; valves somewhat thick, somewhat thicker before ; beaks 

 prominent; epidermis yellowish-olive, very much rayed; cardinal teeth small, 

 compressed and crenulate ; lateral teeth somewhat thick, lamellar and nearly 

 straight ; nacre white and iridescent. 



Proc. Acad. Nat. Sci., 1811, p. 192. 



Hah. — Holston River, East Tennessee, Miss A. E. Law. 



My cabinet, and cabinets of Dr. Lewis, Mr. Wheatley and Miss Law. 

 Diam. -7, Length LI, Breadth 1-4 inch. 



Shell smooth, subtriangular, somewhat inflated, nearly equilateral, rounded 

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

 thicker before; beaks prominent; ligament short, thick and brown; epidermis 

 yellowish-olive, very much rayed, with rather distant marks of growth ; umbonial 

 slope raised and obtusely angular ; posterior slope cordate and generally rayed ; 

 cardinal teeth small, compressed, crenulate and disposed to be treble in the right 

 valve; lateral teeth rather thick, short, lamellar and nearly straight; anterior 

 cicatrices distinct, small and deeply set; posterior cicatrices distinct, small and 

 well impressed; dorsal cicatrices placed above the centre of the cavity of the beaks; 

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

 obtusely angular ; nacre white and iridescent. 



Remarks. — This species is closely allied to tumescens (nobis) in outline, in size 

 and in color of the epidermis. It may, however, be distinguished by radiosus being 

 rather more compressed, having a yellowish epidermis with more rays, which 

 usually are broader and greenish. Some of the specimens are nearly covered with 

 beautiful broad green rays. Tumescens has higher beaks, a darker epidermis and 

 fewer rays. It is also usually thicker in the substance of the shell. None of the 

 beaks of nearly a dozen before me, sent by Miss Law, are perfect enough to show 



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