83 



as I have never found it to vary in a great number 

 of specimens, which is seldom the case in most other 

 species. A variety is remarkably abundant in the 

 Black Warrior river, at Erie, Alabama. 



Mr. Say has referred this species to U. nodulosus, 

 Wood, but the figure of that shell in Wood's Con- 

 chology appears to me to represent a very different 

 species. 



UNIO STEGARIUS. 



Plate XLVL— Fig. 1. 

 DESCRIPTION. 



Shell elevated, ovate; valves thick, with concentric 

 furrows and ridges; disk with a narrow, not deeply 

 impressed furrow from beak to base; umbo and beaks 

 inclining forward; lunule large, ovate-acute, very dis- 

 tinct; beaks pointed and incurved; umbonial slope 

 carinated over the umbo; epidermis yellowish-brown, 

 with crowded, fine, green dotted rays, and broad 

 rays, composed of large dots; posterior margin direct; 

 within white; cardinal plate greatly dilated; cardinal 

 teeth direct, deeply sulcated; muscular impressions 

 small. 



SYNONYMES. 



U. stegaria, Raf. Ann. gen. des Sc. Phys., vol. v. p. 46. 



Poulson's translation, p. 51. Say, Amer. Conch., No. 6. 



Ferr., Mag. de Zool. 

 U. irroratus, Lea. Trans. Amer. Phil. Soc, new series, vol. 



iii. p. 269, pi. v. fig. 5. 

 Cab. A. N. S., No. 1122. 



