DIPI.ODON 1243 



■U- 



ber of specimens, may prove to be only a variety of U. clian\, 

 ana, with which it was found. We collected it in a brook near 

 Maldonado and in the Rio Canelon grande, near Montevideo, 

 Republic of Uruguay. It is rare." 



DiPLODON CHARRUANUS (d'Orbigny). 



Shell decidedly rhomboid, subinliated, solid, finely, concen- 

 trically striate ; epidermis yellowish-brown ; inequilateral, with 

 a high, rounded posterior ridge, which ends behind in a round- 

 ed point at the base line ; beaks rather full and high, strongly 

 radially sculptured ; left valve with a large, much split-up pseu- 

 docardinal and a somewhat double lateral ; right valve having 

 a similar split pseudocardinal and a double lateral; anterior 

 scars impressed ; nacre whitish, blotched in the cavities, thicker 

 in front. 



Length 63. height 35, diam. 24 mm, 



L'ruguay. 

 Unio charruana d'ORBiGNv, Guer. Mag., 1835, P- 35 ; Voy. Am. 



Men. 1843, P- 606, pi. Lxxi, figs. 8-14. 

 Margarita (Unio) charntanns Lua, Syn., 1838, p. 20. 

 Margaron (Unio) charrnanus Lea, Svn.. 1852, p. 29- 1870 



P- 54- 

 Unio cJ'.arruanits Sowerby, Conch. Icon., XVI, 1868, pi. xciii, 



figs- 505. 5050. 505^- 

 Diplodon charrnanus Simpson, Syn., 1900, p. 876. 

 Unio faba d'ORBiGNv, Mag. Zool. 1835, p. 35 ; Voy. Am. Mer.. 



1843. P- 606, pi. LXXI, figs. 8-1 1. 

 Margarita (Unio) faba Lea, Syn., 1838, p. 21. 

 Maro^aron (Unio) faba Lea. Syn.. 1852. p. 31 ; 1870, p. 50. 



More decidedly rhomboid than D. rhnacoicus. The speci- 

 mens in the Lea Collection, which were received from d'Orbig- 

 ny under the name Unio charruana, are young and rather 

 bronzy. In the larger the laterals are partially reversed. 



Diplodon caipira (von Ihering). 



Shell oblong, subsolid, nearly evenly elliptical, subinflated. 

 mequilateral, with a rather full, rounded posterior ridge, which 

 ends behind at or below the median line; beaks moderately 



