NAIADES. MOLLUSCA. UNIO. 107 



Genus IJNIO, Brcg. 



Shell equivalve, inequilateral ; hinge with 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-brown ; interior 

 purple or salmon-colored ; hinge teeth deeply striated, pyramidal. 



Figures 68, 69, 70. 

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



Mya complanata, Solander; Mss., Portland Catal., 100. Dillwyn ; Catal.,i. 



51. 



U^nio parpureus, Say ; JVich. Encyc. (Jlmer. ed.,) iv. 3, f. 1. Deshayes ; Encyc. 



Meth., Vers, ii. 581, pi. 249, f. 5. Barnes ; Silliman's Journ., vi. 216. 

 U'nio purpurascens, Lam., .4n. sans Vert., vi. 535. 

 U^nio violaceus, Spengi.ek. 

 U^nio rarisulcata, coarctata, rhombula, carinifera, Geor^ina, glabrkla and sulci- 



dens of Lam. ; {jln. sans. Vert., vi.) on the authority of Lea. 

 U^nio fluviatilis, Green. 

 U^nio complaniitus, Lea; JYaiades, 30. Trans. Amer. Phil. Soc, (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, 

 httle 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 

 shghtly 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- 



