392 NEW EXOTIC UNIONIDiE. 



general form in the South American species. Besides this roundness of the palpi, 

 there is a peculiarity of the branchiae, — they being all of the same size, — and also of 

 the anal and super-anal opening being ununited. In these specimens there is a deposit 

 on the side of the abdominal sack, in the palpi and along the inferior portion of the 

 mantle, as well as on the dorsal membranes, which is hard and almost stony. This 

 may have been deposited after they were put into alcohol, but it seems to be inside 

 of the membranous matter. 



Anodonta rubicunda. PI. 46, fig. 299. 



Testa alata, lsevi, subrotunda, inflata, subsequilaterali, antice et postice rotundata ; valvulis subtermibus ; 

 natibus elevatis, tumidis, rosaceis ; epidermide tenebroso-rufo-fusca, vel obsolete radiata vel eradiata, 

 margarita rufo-salmoneo colore tincta et valde iridescente. 



Shell winged, smooth, subrotund, inflated, nearly equilateral, rounded before and 

 behind ; valves rather thin ; beaks raised, swollen and rose-colored ; epidermis dark 

 reddish-brown, obsoletely rayed or without rays ; nacre reddish-salmon and very 

 iridescent. 



Ilab. — Uruguay River, Prof. J. Wyman. 



My cabinet. 

 Diam. 1-2, Length 2, Breadth 2-3 inches. 



Shell alate, smooth, subrotund, inflated, subequilateral, rounded behind and before, 

 subangular on the wing and with a slightly-curved dorsal margin ; substance of the 

 shell rather thin ; beaks raised, swollen, rose-colored, apparently without any undu- 

 lations at the tips ; ligament rather short, somewhat thick and partly concealed ; 

 epidermis dark reddish-brown, obsoletely rayed or without rays, and with rather 

 distant marks of growth ; umbonial slope very slightly raised and rounded ; pos- 

 terior slope raised into a wing, with two obscure lines on each valve, from the 

 beaks to the posterior margin ; anterior cicatrices confluent and slightly impressed ; 

 posterior cicatrices confluent and scarcely visible ; dorsal cicatrices invisible ; cavity 

 of the shell deep and rounded ; cavity of the beaks rather shallow and angular ; 

 nacre reddish-salmon, whitish or purplish towards the beaks and very iridescent. 



Remarks. — Two specimens, an adult and a young one, only were obtained by Prof. 

 Wyman. It is near to rotunda, Spix, but is rounder, has a higher wing, is smaller 

 and thinner, and probably is never white in the nacre ; it therefore cannot be con- 

 founded with that species. There is a remarkable redness in this species. The 

 deposit of the base membrane seems to be reddish throughout, while the pearly 

 deposit is white in the adult specimen and purplish in the junior one. Therefore, 

 where the epidermis is worn off, the color is quite red. The adult is without rays, 

 while the junior has very obscure rays. The sinus at the end of the ligament is 

 triangular, as usual with the South American species. 



