394 NEW EXOTIC ILNIONIDjE. 



thicker before ; beaks rather elevated, swollen ; epidermis dark-olive, without rays ; 

 nacre bluish-white and very iridescent. 



Jlab. — Uruguay fiiver, Prof. J. Wyman. 



My cabinet. 

 Diam. 1-6, Length 2-4, Breadth 3'5 inches. 



Shell smooth, obovate, much inflated, very inequilateral, obtusely angular behind 

 and obliquely rounded before ; substance of the shell rather thick, somewhat thicker 

 before ; beaks rather elevated, swollen ; ligament large, rather long and dark-brown ; 

 epidermis dark-olive, without rays, with distant marks of growth ; umbonial slope 

 inflated and rounded ; posterior slope raised into a carina ; with an impressed line 

 from the beaks on each valve to the posterior margin ; anterior cicatrices confluent 

 and somewhat impressed ; posterior cicatrices confluent and very slightly impressed ; 

 dorsal cicatrices invisible ; cavity of the shell very deep and rounded ; cavity of the 

 beaks shallow and angular ; nacre white and very iridescent. 



Remarks. — A single, much worn and imperfect specimen only was brought by 

 Prof. Wyman. It seems to be between Blainvilliana (nobis) and trapezialis, Lam., 

 not being so oblique or transverse as the former, and the substance of the shell is 

 thicker than either. It is more ventricose than either, the larger transverse diame- 

 ter being in the middle of the shell and not towards the beaks. The sinus at the 

 end of the ligament is triangular, as usual with the South American species, but in 

 this specimen it is more acute and inflected than usual. The margin at the base 

 is very wide, but that is not the case anteriorly or posteriorly. The beaks being 

 very imperfect, it is impossible to say what may be the nature of the undulations of 

 the tips, if it has any, 



Anodonta lato-marginata, Lea. 



[From Amer. Philos. Soc, vol. v. pi. 12. Obs. vol. i. page 188.] 



Soft Parts. — Branchial uterus . No ova were found in the only specimen received. 



Probably a female from the form. Branchial large, rounded below, inner one rather 

 the larger, united the whole length of the abdominal sack. Palpi rather large, 

 round, united only at the upper part. Mantle thin, thickened at the edges, with 

 numerous very small papillae below the branchial opening. Branchial opening large, 

 with numerous very small, brown papillae on the inner edges. Anal opening large, 

 with dark-brown edges, not furnished with papillae. Super-anal opening large, not 

 united below. Color of the mass whitish. 



It will be observed that this species is very like to Wymanii in the anatomy, 

 having those remarkable rounded palpi, but they differ much in the outer covering 

 as regards form and color. 



