Descriptions of Fifteen new Species of Uruguayan UNIONIDiE 



BY ISAAC LEA. 



[Read March 13th, I860.] 



During the winter of 1858-59, R. B. Forbes, Esq., of Boston, whose name has 

 been identified with so many works of philanthropy and public utility, organ- 

 ized an excursion to the La Plata, the Uruguay and Rio Negro rivers, in South 

 America ; his object in part being to afford facilities for studying the natural his- 

 tory of the countries bordering on these waters. Professor J. Wyman, who ac- 

 companied him, has most kindly placed at my disposal all the specimens of the 

 Vnionidae which he had been enabled to collecr in these extensive southern fresh 

 waters. In this very interesting collection I was surprised to find so many 

 species which had not been before observed. These are now herein described, 

 and consist of eleven Uniones and four Anodontee. The whole number brought 

 of these fresh water Mitlluscs, was twenty-three species. Those heretofore de- 

 scribed are Prisodon truncalus, Schum., (Castalia ambigua, Lam.,) Unio Para- 

 nensis, Lea., TJ. parallelopipedon, Lea., Anodonta rotunda, Spix, A. trapezalis, Lam., 

 A. lato-marginata, Lea, A. tenebricosa, Lea, A. Blainvilliana, Lea. In addition 

 there were three small species of Cyrena, two of which I have not ascertained, 

 the third is the variegata of D'Orbigny. There was also a small species of 

 Cyelas. 



Unio Wymanii. — Testa laevi, antice subsulcata, quadrata, compressa, ad latere 

 planulata, insequilaterali, postice obtuse angulata, antice rotundata; valvulis 

 subcrassis, antice crassioribus ; natibus prominulis, ad apices divaricate undu- 

 latis; epidermide tenebroso-oliva, vel eradiata vel obsolete radiata; dentibus 

 cardinalibus compressis, erectis, crenulatis, in utroque valvulo duplicibus ; later- 

 alibus longis, crenulatis subcurvisque ; margarita argentea et valde iridescente. 



Hab. — Uruguay River, S. America. Prof. J. Wyman. 



Unio Uruguayensis. — Testa, lsevi, antic6 subsulcata, elliptica, inflata, subequi- 

 laterali, postice obtuse angulata, antice rotundata; valvulis subcrassis, antice 

 crassioribus; natibus subprominentibus, ad apices divaricate undulatis; epi- 

 dermide virido-fuscA, postice tenebricosa, polita, obsolete radiata; dentibus car- 

 dinalibus compressis, crenulatis suberectisque ; lateralibus longis subrectisque ; 

 margarita argentea et iridescente. 



Hab. — Uruguay River, S. America. Prof. J. Wyman. 



Unio piger. — Testa laevi, elliptica, inflata, subequilaterali, postice obtuse an- 

 gulata, antice oblique rotundata; valvulis crassiusculis, antice paulisper eras- 



