388 NEW EXOTIC UNIONIDiE. 



undulatis ; epidermide nigro-fuscfi,, striata, obsolete radiatfi, ; dcntibus eardinalibus comprcssis, 

 crenulatis ; lateralibus sublongis curvisque ; magarita argentea et iridoscente. 



Shell smooth, elliptical, inflated, subequilateral, obtusely angular behind, obliquely 

 rounded before ; valves somewhat thick, slightly thicker before ; beaks rather pro- 

 minent, inflated, with divergent undulations at the tips ; epidermis blackish-brown, 

 striate and obscurely rayed ; cardinal teeth compressed, crenulate ; lateral teeth 

 rather long and curved ; nacre silver-white and iridescent. 



Hob. — Uruguay River, South America, Prof. J. Wyman. 



My cabinet. 

 Diam. 1, Length P5, Breadth 2-2 inches. 



Shell smooth, elliptical, inflated, nearly equilateral, obtusely angular behind and 

 obliquely rounded before ; substance of the shell rather thin, thicker before ; beaks 

 rather prominent, inflated, with divergent undulations at the tips ; ligament short and 

 dark brown; epidermis blackish brown, striate and obscurely rayed, with very indis- 

 tinct somewhat distant marks of growth ; umbonial slope much raised and rounded ; 

 posterior slope wide, obscurely sulcate, dark-brown, almost black ; cardinal teeth com- 

 pressed, crenulate, slightly curved, distinctly double in the right valve and slightly 

 double in the left valve ; lateral teeth rather long and curved ; anterior cicatrices 

 small, well impressed, confluent with the lower but distinct from the upper ; posterior 

 cicatrices rather small, confluent and very slightly impressed ; dorsal cicatrices placed 

 across the centre of the cavity of the beaks ; cavity of the beaks somewhat deep and 

 rounded ; nacre silver-white and iridescent. 



Remarks. — Only a single specimen was brought by Prof. Wyman, and this without 

 perfect beaks. There are points, however, of the divergent costas observable which 

 shew that the usual South American character of the tips of the beaks belong to it. 

 It is nearly allied to Uruguayemis, herein described, but it is a smaller species, rather 

 rounder, has a darker and much less shining epidermis. It belongs to the group of 

 which delodontus, Lam., may be considered the type, but it is not so oblique as that 

 species, and differs altogether in the color of the epidermis. 



Unio Uruguatensis. PI. 45, fig. 298. 



Testa kevi, antice subsulcata, elliptica, inflata, subsequilaterali, postice 1 obtuse angulatS., antice rotundata ; 

 valvulis subcrassis, antice crassioribus ; natibus subproininentibus, ad apices divaricate undulatis ; 

 epidermide virido-fusca, postice tenebricosa, polita, obsolete radiata ; dentibus eardinalibus coni- 

 pressis, crenulatis suberectisque ; lateralibus longis subreetisque ; margarita argentea et iridescente. 



Shell smooth, subsulcate before, elliptical, inflated, subequilateral ; obtusely 

 angular behind, rounded before ; valves rather thick, thicker before ; beaks a little 

 prominent, with divergent undulations at the tips ; epidermis greenish-brown, darker 



