1256 DlPIOnON 



pressed, the posterior one feeble, the two laterals are delicate 

 and lamellar; right valve with two compressed pseudocardinals, 

 the upper small, and one lateral ; nacre bluish-white, a little 

 thicker in front. 



Length 52, height 29, diani. 17 mm. 



Uruguay River. 

 Unio lepidits Lea, Pr. Ac. N. Sci. Phila., IV, i860, p. 91 ; Jl. 



Ac. N. Sci. Phila., V, 1863, p. 390. pi. l, fig. 306; Obs., X,. 



1863, p. 25, pi. I,, fig. 306. 

 Alargaron (Unio) Icpidior LTi^. Svn.. 1870, p. 53. 

 Diplodon Icpidior Simtson, Syn., 1900, p. 880. 



The dorsal and ventral lines are nearly parallel, the anterior 

 end being a trifle narrowed. The surface is smooth and shin- 

 ing, of much the same texture and appearance as many of the 

 forms of this group west of the Andes. First called lepidus 

 by Lea, but changed by him to Icpidior because lepidus had 

 been used by Gould for a Unio. 



DiPLODOiV PARCus (Lea). 



Shell long and nearly evenly elliptical, convex, inequilat- 

 eral, with moderately full beaks, which are elevated a little 

 above the dorsal line, their sculpture about sixteen, rather 

 strong, straight ridges ; posterior ridge moderate, rounded ; 

 growth lines irregular ; epidermis smooth, shining, yellow 

 green, slightly bronzy, with a light median, concentric band ; 

 left valve with one compressed pseudocardinal with a vestige 

 of another behind it and two delicate laterals ; right valve with 

 two pseudocardinals, the upper very small, and one straight 

 lateral ; beak cavities shallow ; nacre pale blue. 



Length T^y, height 18, diam. 14 mm. 



South America. 

 Unio parens Lea. Pr. Ac. N. Sci. Phila., X, 1866, p. 34; Jl.^ 



Ac. N. Sci. Phila., VL 1S68. p. 262, pi. xxxiii, fig. yy \ Obs., 



XIL 1869, p. 22, pi. xxxTiT, fig. yy. 

 MarQ;aron (Unio) paresis Lea, Syn., 1870, p. 47. 

 Diplodon parens Simpson, Syn., 1900, p. 880. 



Probably a young shell. Tt is more inflated than most mem- 

 bers of this group, but it has the smooth, bronzy epidermis of 

 manv of it? members. 



