12 28 Dipr,onoN 



DiPLODON WHEATLEYANUS (Lea). 



Shell subrhoniboid. subinflated, solid, inequilateral ; beaks 

 not full or high, sculptured with very strong, radial ridges ; 

 posterior ridge well developed, subangular. ending below in 

 a blunt point near the base of the shell ; surface rudely and 

 unevenly, concentrically sculptured, with traces of radial sculp- 

 ture, somewhat plicate on the posterior slope ; epidermis brown- 

 ish-green, sub-shining : left valve with two subcompressed, 

 ragged pseudocardinals and two laterals, the inner higher; 

 right valve with two pseudocardinals, the upper small and 

 compressed, and one somewhat double lateral ; dorsal scars 

 numerous and deep ; anterior adductor scars small, behind 

 them a deep crescentic scar on the base of the pseudocardinals ; 

 nacre white, slightly thicker in front. 



Length 70, height 47, diam. 30 mm. 



Argentina. 

 Unio u'hcatleyanus Lea, Pr. Ac. N. Sci. Phila., VIII, 1856, p. 



94; Obs.. VI, 1857, p. 28, pi. XXIX, fig. 23; Jl. Ac. N. Sci. 



Phila., 1858, p. 308, pi. XXIX, fig. 23. — SowERBY, Conch. 



Icon., XVI, 1868, pi. XL, fig. 487. 

 Margaron (Unio) 7vheatleyainis Lea, Syn., 1870, p. 50. 

 Diplodon whcatleyanus Simpson, Syn., 1900, p. 875. 



DiPi.ODON RHOMBEUS (Wagner). 



"Shell round-ovate or oblong^ovate, inflated in front, nar- 

 row behind, solid, transversely striate or sulcate ; anterior end 

 neither angulate nor plicate. Dorsal margin oblique, curved ; 

 beaks anterior, not very high. Anterior margin obliquely trun- 

 cate, posterior rounded. Llinge curved ; cardinal tooth heavy, 

 compressed, bifid, striate ; laterals substriate, single in the left 

 valve, double in the right. Beaks depressed, eroded. LTmbones 

 plano-convex. Interior of the shell smooth, shining, pearly. 

 Posterior muscular impression distinct, with two smaller ones 

 adjacent, anterior shallow. Epidermis brown; nacre bluish- 

 white. 



Length 3, lieight 2.1 inches." (Wagner). 



Brazil. 



