226 DESCRIPTION OF 



cicatrices confluent; dorsal cicatrices none; cavity of the shell rather deep and 

 rounded; cavity of the beaks shallow; dorsal line rather curved; nacre bluish- 

 v^^hite and iridescent. 



Remarks. — Tvt^o perfect individuals, and two valves of this species were re- 

 ceived among other specimens of the Naiades from Dr. Foot of the United 

 States Army. This species seems to be allied to An.fragilis, Lam., but is a 

 larger and stronger shell. The lines of growth are distinct and very close 

 together. 



Anodonta Maryattana. Plate 20, Fig. 45. 



Testa transversa, valdh injlatd, gibbosd, valde inaquilaterali; valvulis tenuibus; natibus prominen- 

 tibus, ad apices undulatis; epidermide virido-luted; margaritd argented et iridescente. 



Shell wide, very much inflated, gibbous, very inequilateral; valves thin; beaks prominent, undulated at 

 the tip; epidermis greenish yellow; nacre silvery and iridescent. 



Hab. Vicinity of Fort Winnebago. Capt. Maryatt, R. N. 



My Cabinet. 

 Diam. 1.8, Length 2.2, Breadth 4 inches. 



Shell wide, very much inflated, gibbous, very inequilateral; substance of the 

 shell very thin and transparent; beaks prominent and doubly undulate at the 

 tip; ligament thin and long; epidermis greenish-yellow; anterior cicatrices con- 

 fluent; posterior cicatrices confluent; dorsal cicatrices none; cavity of the shell 

 very deep; cavity of the beaks rather deep and rounded; dorsal line slightly 

 curved; nacre silvery and iridescent. 



Remarks. — Among many fine specimens of the Naiades brought by Capt. 

 Maryatt from a tour up the Mississippi, &c., was a single specimen of this 

 Anodonta. It is more inflated than any species I am acquainted with except 

 the An. gihhosa, Say. Like it, it has that irregular swelling over the portion 

 embracing the umbonial slope. It differs in being more transverse, and being 

 devoid of rays. The nacre is remarkably thin, silvery and iridescent. The 

 marks of growth are very distinct and widely separate. 



