NEW FRESH WATER AND LAND SHELLS. 193 



Remarks. — This is among the most remarkable species of Unio which have 

 come under my notice. It resembles U. monodontus, (Say) in outline as well 

 as in the imperfection of the cardinal and lateral teeth, both of which, how- 

 ever, are more perfect in the JJ. cucumoides. In the specimen before me there 

 is a deep muscular impression above and distinct from the great anterior cica- 

 trix. This is nearly round and penetrates the base of the cardinal tooth. It 

 may be that it is formed by a branch of the anterior adductor muscle. An 

 examination of the animal only can decide this point. In the above descrip- 

 tion it will be observed that the anterior cicatrices are described as beino- con- 

 fluent. This alludes to the cicatrices of the adductor muscle and the muscle 

 of locomotion as usual. The third cicatrix of the anterior part is now, I believe, 

 for the first time observed. The dorsal and basal margin are nearly parallel 

 The nacre is stained with epidermal matter as it usually is in shells of this 

 form. 



This specimen was kindly lent to me for description by Dr. Jay, who received 

 but a single one from Sidney, New South Wales. In its general form and 

 tuberculate exterior it resembles a cucumber. 



Unio cuneolus. Plate 7, Fig. 3. 



Testa triangulari, compressd, valdt inaquilaterali; valvulis subcrassis; natihus elevalis ; epidermide 

 luted, striata, radiis maculatis ; dentibus cardinalibus parvis; later alibus longis rectisque; margaritd 

 alba et iridescente. 



Shell triangular, compressed, very inequilateral; valves rather thick; beaks elevated; epidermis yellow, 

 striate, with spotted rays ; cardinal teeth small; lateral teeth long and straight; nacre white and iridescent. 



Hab. Holston River, Tenn. Mr. S. M. Edgar. 



My Cabinet, and Cabinets of Mr, Edgar and Dr. Currey. 

 Diam. .6, Length 1, Breadth 1.4 inches. 



Shell triangular, compressed, flattened on the sides, very inequilateral; sub- 

 stance of the shell thick before, thinner behind; beaks elevated ; ligament short 

 and thin; epidermis yellow, striate, with numerous green interrupted rays over 

 the whole disk; cardinal teeth small, single in the right valve and double in 

 the left; lateral teeth long and straight; anterior cicatrices distinct; posterior 

 cicatrices distinct; dorsal cicatrices placed on the under side of the cardinal 



