380 NEW EXOTIC UNIONID^. 



Hal). — Uruguay River, South America, Prof. J. Wyman. 



My cabinet and cabinet of C. M. Wheatley. 

 Diam. *7, Length 1:1, Breadth 1*8 inch. 



Shell smooth, elliptical, somewhat inflated, very inequilateral, somewhat rounded 

 behind and obliquely rounded before ; substance of the shell somewhat thick, slightly 

 thicker before; beaks slightly prominent; ligament small and dark-brown; epi- 

 dermis shining, black, striate and obscurely rayed, with rather distant marks of 

 growth ; umbonial slope somewhat raised and rounded ; posterior slope compressed, 

 elliptical, with an obscure furrow on each valve ; cardinal teeth rather small, 

 compressed, lamellar, oblique, single in the left and double in the right valve ; lateral 

 teeth rather long, somewhat thin and curved ; anterior cicatrices rather small, well 

 'impressed, confluent with the lower but distinct from the upper ; posterior cicatrices 

 confluent, rather large and slightly impressed; dorsal cicatrices well impressed, and 

 placed across the cavity of the beaks ; cavity of the shell rather deep and wide ; 

 cavity of the beaks shallow and rounded ; nacre bluish white and iridescent. 



Remarks. — There were three specimens among the shells from Prof. "Wyman. 

 They all differ slightly in the ellipticity of outline. One being a little wider and 

 the other not quite so much so as that figured. It is very near to lugubris (nobis) in 

 outline and in the blackness of the epidermis, but in the nacre it differs entirely, 

 as it dees in the cardinal teeth. It is also very near in outline to lepidus, herein 

 described. The single cardinal tooth in the left valve is very unusual. The black- 

 ness of the epidermis is very striking and apparently it is without rays. In looking 

 through the valve the hue is greenish, and one of the specimens exhibits obscure 

 rays. The beaks of all the three are eroded, and I cannot therefore describe the 

 undulations of the tips. From indications in the exposed nacre I have no doubt 

 that this species has diverging undulations at the tips. The transverse striae are 

 coarse, almost amounting to sulcations. The cardinal are nearly on the same curve 

 with the lateral teeth. 



Unio nocturnus. PI. 42, fig. 288. 



Testa losvi, subrotunda, subconipressa, inasquilaterali, antice et postice rotvmdata ; valvulis cvassis, antice 

 crassioribus ; natibus proniinulis, subinflatis ; epidormide nigricante, antice rugoso-striatS,, eradiata ; 

 dentibus cardinalibus parviusculis, erectis, subcompressis, in utroque valvule- duplicibus; lateralibus 

 sublongis valde curvisque; margarita vel alba vel salmonis colore tineta. 



Shell smooth, subrotund, somewhat compressed, inequilateral, rounded before and 

 behind ; valves thick, thicker before ; beaks somewhat prominent and a little in- 

 flated ; epidermis blackish, roughly striate before and without rays ; cardinal teeth 

 rather small, erect, rather compressed, double in both valves; lateral teeth rather 

 long and much curved ; nacre white or salmon color. 



