﻿EXOTIC UNIONIDiE. 241 



alae posterioris basi apiceque uudulatis, natibus compressis, ad apicem undulatis, haud prominentibus ; 

 epidermide nitida, tenebroso-viridi et tota radiata; dentibus cardinalibus parviusculis, compressis, in 

 utroque valvulo duplicibus efc cermiis; lateralibus longissimis, lamellatis subcurvisque ; liganiento 

 celato; niargarita alba et valde iridescente. 



Shell double winged, plicate, triangular, very much compressed, angular be- 

 hind, very inequilateral ; posterior wing high, acuminate, crenulate on the margin ; 

 valves rather thin, connate before and behind the beak ; beaks compressed, not 

 prominent, undulate to the tip ; the base and summit of the posterior wing undu- 

 lated ; epidermis shining, dark green radiated all over; cardinal teeth rather- 

 small, compressed, double in both valves and inclined downwards ; lateral teeth very 

 long, lamellar and somewhat curved ; ligament concealed ; nacre white and beauti- 

 fully iridescent. 



Unio Cumingi.l, Lea. Proc. Acad. Nat. Sci., Vol. 6, p. 54. 



Hub. — Northern pnrt of China. H. Cuming. 



My cabinet and cabinet of Mr. Cuming, London. 

 Diam. 1, Length 4-5, Breadth 52 inches. 



Shell double winged, folded on the side and behind the umbonial slope, triangular, 

 very much compressed, angular behind, very inequilateral; posterior wing high, 

 acuminate, crenulate on the superior margin ; anterior wing very small and slightly 

 elevated ; substance of the shell rather thin, connate before and behind the beaks ; 

 beaks, as well as the base and summit of the posterior wing, undulated ; compressed, 

 undulated at tip, not prominent; ligament concealed; epidermis smooth and shining, 

 dark green, radiated all over, even to the extremity of the wing, with distant marks 

 of growth; umbonial slope slightly elevated and rounded; posterior slope raised into 

 a high wing; cardinal teeth rather small, compressed, double in both valves and 

 inclining downwards ; lateral teeth very long, lamellar and somewhat curved, single 

 in the right and double in the left valve ; anterior cicatrices small, the superior and 

 lateral smaller ones both distinct from the large one ; posterior cicatrices confluent 

 and indistinct; dorsal cicatrices small, placed obliquely across the cavity of the beak ; 

 palleal cicatrix well impressed and very distant from the margin of the disk ; cavity 

 of the shell extremely shallow ; cavity of the beaks scarcely perceptible; nacre white 

 and richly iridescent. 



Remarlcs. — This very beautiful and rare Unio is, in form and general outline, very 

 much like the Dipsas plicatus, Leach, but they cannot be confounded with each other, 

 as they belong to very distinct genera, the Dipsas having but one linear tooth in 

 each valve, while the above described shell has perfectly well denned, compressed, 

 cardinal teeth, double in both valves. It also has long lateral, lamellar teeth, double 

 in the left and single in the right valve. It differs also in the folds, having them 

 extending over the flattened side from the beaks, becoming lower and more obscure 



