﻿EXOTIC UNIONIDiE. 245 



Remarks. — Two specimens are before me. The more perfect and smaller one is 

 figured. Both are much eroded at the beaks, hence that part is not described. I 

 have no doubt, however, that the folds, which commence about half way from the 

 basal margin are, in perfect specimens, continued to the apex, where they may 

 assume the form of granules or very small plications. In young and perfect speci- 

 mens the epidermis towards the beaks will probably be found to be greenish, as the 

 better specimen of the two indicates. It is perhaps nearest to ellipticus (nobis) lean- 

 ing towards Hembeli, Con. It is more compressed than the former and not so wide as 

 the latter, and in the folds it differs from both. 



Unio navigioliformis. PI. 37, fig. 124. 



Testa minute plicata, valde oblcmga, subinflata, valde insequilaterali, postice truncata et subemarginata, ad 

 basim emarginata, antice ovato-rotundatii ; Yalvulis crassiusculis ; natibus prominulis ; epidermide 

 tenebroso-fusca, eradiata, micante ; dentibus cardinalibus crassiusculis, obliquis, compressis, in utroque 

 valvule- duplicibus ; lateralibus prtelongis subcurvisque ; margarita alba et iridescente. 



Shell minutely plicate, very oblong, somewhat inflated, very inequilateral, truncate 

 and subemarginate behind, emarginate at base, ovately rounded before; valves some- 

 what thick ; beaks slightly prominent ; epidermis dark brown, without rays, shining ; 

 cardinal teeth somewhat thick, oblique, compressed and double in both valves ; 

 lateral teeth very long and slightly curved ; nacre white and iridescent. 



Unio navigioliformis, Lea. Proc. Acad. Nat. Sci. ; 1859, p. 152. 



Hah. ? H. Cuming. 



Cabinet of Mr. Cuming. 

 Diam. *6, Length 1, Breadth 2-1 inches. 



Shell w r ith small folds, very oblong, somewhat inflated, very inequilateral, truncate 

 and subemarginate behind, emarginate at base, ovately rounded before ; substance of 

 the shell somewhat thick ; beaks slightly prominent ; ligament very long, thin and 

 dark brown ; epidermis dark brown, without rays, shining, with regular transverse 

 strige, which cut very minute perpendicular folds and give the side a subgranular 

 appearance ; umbonial slope somewhat raised and rounded ; posterior slope nearly 

 filled with oblique rays and having an impressed line from each beak to the margin, 

 where the valves are open ; cardinal teeth somewhat thick, oblique, compressed and 

 double in both valves ; lateral teeth very long and somewhat curved ; anterior 

 cicatrices confluent, as regards the lower one, but distinct from the upper one ; 

 posterior cicatrices confluent ; dorsal cicatrices 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 white and iridescent. 



Remarks. — Mr. Cuming has no idea of the habitat of this species, a single specimen 

 only of which he obtained. I am disposed to think that it is from South America. 

 It reminds one of U. parallelopipedon, (nobis,) but is not so wide nor so oblique, and 



