I 



EXOTIC UNIONID/E. on 



Shell smooth, oblong, somewhat inflated, nearly equilateral, rounded behind and 

 obliquely rounded before ; sul)stance of the shell rather thick, thicker before ; beaks 

 rather prominent and undulate at the tips ; ligament rather long, somewhat thick 

 and light brown ; epidermis yellowish brown, striate, sulcata on the anterior portion, 

 without rays, darker on the posterior slope ; umbonial slope very much rounded ; 

 dorsal line has a slight callus under the beak ; anterior cicatrices distinct and well 

 impressed ; posterior cicatrices confluent and very large ; dorsal cicatrices deep and 

 placed in a row across the cavity of the beaks ; cavity of the shell rather deep and 

 wide ; cavity of the beaks very shallow and rounded ; nacre whitish or purple and 

 salmon color and iridescent. 



Remarks. — It is rare to meet with an Anodonta of the thickness of this species, but 

 still it is not so ponderous as the arcxwda, Fer., or as lato-marfjinaUi, (noljis). It 

 cannot be confounded with either of these species, not being arcuate, and not having 

 compressed beaks like the former, and being oblong and thinner than the latter, as 

 well as also being destitute of the broad margin. The substance of the shell is slightly 

 thickened anteriorly, and the basal margin is emarginate ; the beaks are submedial, 

 and, when perfect, are beautifully ornate, with numerous small folds, which form an 

 {icute augle from the point of the beaks, nearly parallel to the line of the umbonial 

 slope. The color of a single young specimen before me is salmon inclining to purple, 

 and the adults have the cavity of the beaks tinted in this manner. In the young 

 specimen the lamellar line on the dorsal margin is very well defined, in the adults 

 this character is nearly obliterated. 



Anodonta tenuis. PL 33, fig. 116. 



Tcstil Irevi, obovata, ad later^ valdfe compressa, inaequilaterali ; valvulis pertenuibus ; natibus subpronii- 

 ncntibus, ad apices undulatis ; epidermide tenebroso-fusca, obsolete radiatfi, striata ; raargarita 

 purpurea et vald6 iridescentc. 



Shell smooth, obovate, very much compressed at the side, inequilateral; valves 

 very thin ; beaks a little prominent, undulate at the tips ; epidermis dark brown, 

 obsoletely radiate and striate ; nacre purple and very iridescent. 



Anorlonta tenuis, Lea. Proc. Zool. Soc, Lond., 1850, p. 198. 



Hah. — Sual, Luzon, Philippines. H. Cuming. 

 Diam. 1, Length 17, Breadth 3 inches. 



Shell smooth, obovate, very much compressed at the side ; inequilateral, widely 

 rounded behind ; substance of the shell very thin, slightly thickened before ; beaks a 

 little prominent, minutely undulate at the tips ; ligament rather large, thin aad light 

 brown; epidermis dark brown, obsoletely radiate, striate, and with rather distant 

 lines of growth; umbonial slope raised and much rounded; posterior slope dark 

 brown, raised into a carina ; anterior cicatrices distinct and but slightly impressed ; 



