" UNITED STATES AND ARCTIC AMERICA. 201 



both valves ; lateral teeth very long, lamellar, oblique and nearly .straight; nacre 

 white and very iridescent. 



Proc. Acad. Nat. Sci., 1861, p. 391. 



Hah. — North Carolina, J. G. Anthony. 



My cabinet and cabinet of Mr. Anthony. 

 Diam. 1-1, Length 1*9, Breadth 3*8 inches. 



Shell smooth, suboblong, very much compressed, flattened at the sides, inequi- 

 lateral, obtusely biangular behind, rounded before ; substance of the shell rather 

 thick, slightly thicker before ; beaks slightly prominent ; ligament long, thick and 

 brown ; epidermis reddish brown or dark brown, transversely striate, with distant 

 lines of growth, scaly below, obscurely rayed ; umbonial slope slightly raised and 

 rounded ; posterior slope narrow, elliptical, carinate, with an impressed line ; cardinal 

 teeth rather large, compressed, striate, slightly double in the right as it is in the 

 left valve ; anterior cicatrices distinct, exceedingly large, rough and well impressed ; 

 posterior cicatrices confluent, large and moderately impressed; dorsal cicatrices 

 placed immediately over the centre of the cavity of the beaks ; cavity of the shell 

 very shallow and very wide ; cavity of the beaks very shallow and rounded ; nacre 

 white and very iridescent. 



Remarks. — Two specimens were sent to me by Mr. Anthony. The beaks of both 

 much eroded, and therefore the undulations cannot be noticed. The larger is a 

 reddish brown, the other a dark brown. In outline this species is closely allied to 

 fumaius, (nobis,) but that is a smaller species, and has a smooth, close, nearly black 

 epidermis, while squameus is roughly striate below and squamose, like percoarctatw, 

 (nobis,) but not quite to such an extent, nor is it quite so much flattened at the sides 

 as percoarctatus, while it is more inclined to be elliptical. It is also thicker in the 

 substance of the valves and has larger teeth. Both the specimens have white nacre. 

 The cardinal teeth have the cleft nearly perpendicular. 



Unio rostrum. PL 29, fig. 270. 



Testa lsevi, subtriangulari, ad latere planulata, valde insequilaterali, postice subbiangulata, antice 

 rotunda ; valvulis crassiusculis, antice paulisper crassioribus ; natibus prominulis ; epidermide 

 teuebroso-fusca, nigricante, eradiata ; dentibus cardinalibus parvis, sulcatis, crenulatis, in utroque 

 valvule- duplicibus ; lateralibus longis, lamellatis subcurvisque ; margarita albida et iridescente. 



Shell smooth, subtriangular, flattened at the side, very inequilateral, subbiangular 

 behind, round before ; valves somewhat thick, slightly thicker before ; beaks slightly 

 prominent ; epidermis dark brown, nearly black, without rays ; cardinal teeth small, 

 sulcate, crenulate, double in both valves ; lateral teeth long, lamellar and somewhat 

 curved ; nacre whitish and iridescent. 



Proc. Acad. Nat. Sci., 1861, p 391 



