NAIADES. MOLLUSCA. ' UNIO. 107 



Genus UNIO, Brlg. 



)S/ie// equivalve, inequilateral ; hinge ivitli a stout, irregular, 

 striated, simple or divided cardinal tooth, in each valve, and an 

 elongated, compressed, lateral tooth extending along the margin. 



Unio complana'tus. 



Shell transversely ovate, somewhat angular posteriorly, inequi- 

 lateral ; beaks not much elevated, epidermis dark-broivn ; interior 

 piuyle or salmon-colored ; hinge teeth deeply striated, jjyramidal. 



Figures 68, 69, 70. 

 State Coll., No. 176. Soc. Cab., No. 2150. 



Mya coinplanata, Solander; Mss., Portland CataL, 100. Dillwyn ; Catal.,i. 



51. 

 U^nio purpureas, Say ; JVich. Encyc. {Jlmer. cd.,) iv. 3. f. 1. Deshaves ; Encyc. 



Mitli., Vers, ii. 581, pi. 249, f. 5. Barnes ; Siliiman's Journ., vi. 21G. 

 U'nio purpurascens, Lam., An. suns Vert., vi. 535. 

 Uhiio violaceus, Spengi.er. 

 U*nio rarisulciita, coarctata, rhoinbula, carinifera, Georgina, glabrcita and sulci- 



dens of Lam. ; (An. sa7is. Vert., vi.) on the authority of Lea. 

 U^nio fluviatilis, Green. 

 U^nio complanatus, Lea; JVdiades, 30. Trans. Amer. Phil. 6'oc., (New Series,) 



iii. 41G, vi. 130, not of Deshayes. 



Shell very variable in form, usually oblong-ovate, sometimes 

 sub-rhomboidal or sub-oval, very inequilateral, broadest behind, 

 rather compressed. Beaks about the anterior fourth of the shell, 

 little elevated, always much eroded, and exhibiting numerous 

 layers of greenish epidermal matter ; anterior extremity always 

 regularly rounded ; superior margin, behind the beaks, straight and 

 somewhat ascending for one half its length, then, suddenly declin- 

 ing, it forms an indefinite angle ; posterior end pointed, rounded or 

 slightly clipped ; inferior margin regularly curved, or sometimes a 

 little arched at the middle ; an obtuse ridge passes from the beaks 

 to the posterior tip. Surface coarsely wrinkled by the lines of 

 growth, and covered by a dark, tar-colored, or very dark-green 

 epidermis. Interior usually of a beautiful dark peach-blossom 

 color, and passes from this through salmon-color to mother-of- 



