NAIADES. MOLLUSC A. UNIO. Ill 



flesh-colored tints. Cardinal teeth erect, triangular, pyramidal, 

 strengthened by a stout rib behind the anterior muscular impres- 

 sion. Length 3 inches, height 1 T 7 7 inch, breadth 1 j inch. 



This is one of our common species, and is to be found in most 

 of the large streams and ponds. It is also one of the shells con- 

 fined to the eastern slope of the range of Alleghanies. 



;; fl- 

 it exhibits but little variation in form, except the usual one, that 



those inhabited by the female are broader behind than those inhabited 

 by the male. 



No species is now better established than the one above described, 

 though there is good reason to believe that the U. radidtus of Barnes, 

 Dillwyn, Wood, and perhaps Say, was the young of either U. cariosus 

 or U. ockraceus, or both. It is most likely to be confounded with U. 

 siliquoideus ; but that shell has the epidermis lighter colored, very 

 closely adhering, and perfectly smooth and glossy ; the teeth also are 

 more compressed and more oblique. Mr. Barnes observes of it that, 

 " amidst a variety almost infinite, like that of the human countenance, 

 there is still a characteristic identity of this species, which can scarcely 

 be mistaken by an experienced observer. One variety of radidtus 

 approaches nearest to this species, but the least appearance of rays 

 forbids its association." This last remark is far from being just. 



UNIO CARIOSUS. 



Shell ovate, inflated, not very thick, inequilateral, beaks rather 

 prominent ; epidermis yellowish-olive, usually radiated with dark- 

 green y within usually bluish-white ; teeth compressed, oblique. 



FIGURE, 72. 

 State Coll., No. 179. Soc. Cab., No. 2354. 



tPnio cariosus, SAY ; Jfich. Encyc. (Amer. ed.) iv. pi. 3, f. 2. BARNES ; Silli- 

 maris Journ.,vi. 271. LEA ; Trans. Amer. Phil. Soc., (New Series,) vi. 126, pi. 

 15, f. 45. (animal). Synops. Naiad., 23. 



tPnio cariosa, LAM ; An. sans Vert., vi. 545. 



tTnio ovata, VALENC. ; Recuett d'Obs. de Zool. par Humb. et Bonpl, ii. 226, pi. 

 50, f. 1. 



tPnio cariosus, CONRAD ; Unionidce, 40, pi. 19. 



Musculus latior subfuscus, cceruleis lineis radiatus, LISTER ; Conch., 152, f. 7. 



Shell very variable in form, ovate, or rounded, moderately 



