﻿EXOTIC UNIONIDiE. 251 



rounded behind, slightly emarginate at base ; valves thin ; beaks small, slightly 

 prominent ; epidermis yellowish olive, minutely and transversely striate, without rays ; 

 cardinal teeth small, oblique, compressed and double in both valves ; lateral teeth 

 long and nearly straight ; nacre bluish white and iridescent. 



Unio fluctiger, Lea. Proc. Acad. Nat. Sci., 1859, p. 152. 



Hah.- ? H. Cuming. 



Cabinet of Mr. Cuming. 

 Diam. -4, Length -7, Breadth 1*3 inch. 



Shell folded all over, rather transverse, compressed, very inequilateral, rather 

 rounded behind, slightly emarginate at base; substance of the shell thin, thicker 

 before ; beaks small, slightly prominent ; ligament rather long, very thin and olive 

 color ; epidermis yellowish olive, minutely and transversely striate, without rays ; the 

 folds, which cover the whole disk, diverge from the point of the beak and extend to 

 the margin, except in the middle, where, coming together, they form a very acute 

 angle, and all are visible on the interior 5 umbonial slope slightly raised and rounded ; 

 posterior slope raised into a small keel ; cardinal teeth small, oblique, compressed, 

 crenulate and double in both valves ; lateral teeth long and nearly straight ; anterior 

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

 posterior cicatrices confluent ; dorsal cicatrices placed in the centre of the cavity of 

 the beaks ; cavity of the shell very shallow ; cavity of the beaks very shallow and 

 rounded; nacre bluish white and iridescent. 



Remarks. — The habitat of this species is unknown to Mr. Cuming, who has but a 

 single specimen. It appears to me to belong to the South American types. In some 

 respects it is very like to scobinatus, (nobis), from Siam, but it is a much thinner 

 shell, more compressed and although covered with folds like that species, the character 

 of them is very different, not being green, and they also diverge differently, 

 particularly on the posterior slope. In this specimen the folds are more distinctly 

 marked in the interior than in any species I have seen, as every one may be perfectly 

 traced there. It has some resemblance to gratiosus, Phili., and crispatus, Gould, but 

 is wider than either and more covered with folds. 



Unio Sikkimensis. PI. 39, fig. 131. 



Testa lsevi, obovata, insequilaterali, subinflata, postice obtuse biangulata ; valvulis crassiusculis • natibus 

 prominulis; epidermide luteo-fusca, eradiata ; dentibus cardinalibus parvulis, brevibus, crenulatis in 

 utroque valvulo duplicibus; lateralibus brevibus subcurvisque ; margarit& alba et iridescente. 



Shell smooth, obovate, inequilateral, rather inflated, obtusely biangular behind • 

 valves a little thickened; beaks slightly prominent; epidermis yellowish brown 

 without rays ; cardinal teeth small, short, crenulate and double in both valves • 

 lateral teeth short and somewhat curved ; nacre white and iridescent. 



Unio Siklnmensis, Lea. Proc. Acad. Nat. Sci., 1859, p. 151. 



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