194 DESCRIPTION OF 



tooth, cavity of the shell small : cavity of the beak angular and rather deep; 

 nacre white and very iridescent. 



Remarks. — I have before me two specimens of this species brought by Mr, 

 Edgar from Tennessee. In form and size it approaches the U. Barnesianus 

 (nobis,) but is more triangular, more flattened on the sides and has the marks 

 of growth closer. 



Unio Cincinnatiensis. Plate 8, Fig. 4. 



Testa nodosa, quadrata, inflatd, emarginata, inaquilaterali; valvulis crassis; natibus elevatis; epi- 

 derdime luted, valde radiatd; dentibus cardinalibus subgrandibus ; lateralibus sublongis rectisque ; mar- 

 garitd alba. 



Shell nodulous, quadrate, inflated, emarginate, inequilateral; valves thick; beaks elevated; epidermis yel- 

 low, much rayed; cardinal teeth rather large; lateral teeth rather long and straight; nacre white. 



Hab. Ohio River at Cincinnati. T. G. Lea. 



My Cabinet, and Cabinet of T. G. Lea. 

 Diam. 1.2, Length 1.5, Breadth 1.9 inches. 



Shell with a row of nodules from the beak to the basal margin, quadrate, 

 inflated, emarginate at basal and posterior margins, inequilateral; substance of 

 the shell very thick, thinner before; beaks large and elevated; ligament short 

 and thin; epidermis yellow, with numerous green capillary rays over the whole 

 disk; cardinal teeth rather large, double in both valves; lateral teeth rather 

 long, thick and straight; anterior cicatrices distinct; posterior cicatrices con- 

 fluent: dorsal cicatrices placed on the under side of the cardinal tooth; cavity of 

 the shell rather deep ; cavity of the beak small and angular ; nacre milky white. 



Remarks. — This is a very rare species. A very imperfect specimen was sent 

 to me by my brother more than ten years since. I then thought that it might 

 be a variety of the species which I afterwards called U.perplexus, Since then I 

 have seen seven specimens, and their constant difference from the perplexus 

 clearly marks their specific distinction. It is very closely allied to another 

 species described by Mr. Conrad under the name of U. PhiUipsii. It differs 

 from it, however, in having the tubercles in a more regular manner arranged 

 over the medial part of the disk. 



