DIPI.ODON 1237 



lower higher ; right valve with two curved, lamellar pseudo- 

 cardinals, the upper small, and one lateral ; dorsal scars large ; 

 muscle impressions shallow ; nacre bluish-white. 



Lengh 55, height 40, diam. 25 mm. 



Uruguay River, South America. 

 Unio pigcr Lu a, Pr. Ac. N. Sci. Phila., IV, i860, p. 90 ; Jl. Ac. 



N. Sci. Phila., Y, 1863, p. 387, pi. xlv, fig. 296; Obs., X, p. 



23, pi. XLV^ fig. 296. — ^SowERBY, Conch. Icon., XVI, 1868, 



pi. Lxxxiv, fig. 449. 

 Margarnn fVnio) pigcr Lea, Syn., 1870, p. 46. 

 DiplodoH piger Simpson, Syn., 1900, p. 875. 



A neat, subinflated, finely concentrically sculptured species. 



DiTEODON PRUNoiDES (Lea). 



"Shell smooth, elliptical, very ventricose, inequilateral, 

 rounded before and behind ; substance of the shell rather 

 thick, somewhat thicker before; beaks somewhat prominent; 

 ligament rather short and thin ; epidermis dark brown, with- 

 out rays ; umbonal slope raised and rounded ; posterior slope 

 wide and cordate ; cardinal teeth compressed, oblique and very 

 much crenulate, double in the right and disposed to be treble 

 in the left valve ; lateral teeth long, lamellar and corrugate ; 

 anterior cicatrices confluent, rather small and well impressed ; 

 posterior cicatrices confluent and slightly impressed ; dorsal 

 cicatrices placed nearly in the centre of the cavity of the beaks ; 

 cavity of the shell very deep and rounded ; cavity of the beaks 

 deep and rounded : nacre silver-white. 



Length 2, height 1.3, diam. i.i in." (Lea). 



South America. ? 

 Unio prunoidcs Lea, Pr. Ac. N. Sci. Phila.. XII, 1868, p. 150; 



Jl. Ac. N. Sci. Phila., VI, 1868, p. 323, pi. liii, fig. 136; Obs., 



XII. 1869, p. 83, pi. 1,111, fig. 136. 

 Margaron (Unio) prunoides Lea, Syn.. 1870, p. 47. 

 Diplodon prunoidcs SrMP.soN, Syn.. 1900, p. 875. 



"A single specimen, which was found among several of U. 

 corriigata Lam. in the collection of the Academy of Natural 

 Sciences. I have little doubt but that it is a native of some of 



