624 MEMOIRS OF THE CARNEGIE MUSEUM. 



62. Anodontites riograndensis (Von Ihering) (1890). 

 Shells: Plate XLIII, figs. 2, 3; Plate XLIV, fig. 2. 

 Anodonta riograndensis Von Ihering, 1890, pp. 154, 158. 

 Glnbaris riograndensis Von IherinG; 1893, pp. 118, 119. 

 Anodonta exotica Corsi {non Lamarck), 1901, j). 456, fig. 37. 



It is quite possible that A. exotica of D'Orbigny {nan Lamarck) represents 

 chiefly this species. However, on account of the great diameter (44 pr. ct. of length) 

 of the specimen measured, this appears to be rather A. forbcsiana. Since there is 

 no figure given, D'Orbigny's species remains doubtful. The figure of A. exotica 

 given by Corsi certainly in this species. 



Type-locality. — Rio Grande do Sul, Brazil. 



Other Localities. — Rio Paraguay (Von Ihering); Lower Parana and La Plata 

 Rivers (Von Ihering) ; Rio LTruguay (Von Ihering) ; Department of Colonia, Uruguay 

 (Corsi); Arroyo Mendoza, Department Florida, Uruguay (Corsi); Montevideo, 

 Uruguay (Von Ihering). 



New Localities. — In a pond along banks of the Rio Negro, Santa Isabel, 

 Uruguay (J. D. Haseman coll., February 11, 1909). Two males with soft parts, 

 four odd right vales. Headwaters of Rio Paraguay, Santa Rita, Matto Grosso, 

 Brazil (J. D. Haseman coll., June 12, 1909). One specimen. Rio de la Plata, 

 San Isidro, 20 km. N. of Buenos Aires, Argentina (A. Windhauscn coll., January 

 1917). Three specimens, male, and gravid females, with soft parts. 



Distribution. — La Plata-drainage from Buenos Aires up to the headwaters of 

 the Paraguay in Matto Grosso; in the Uruguay and its tributaries; and also in 

 streams of the Banda Oriental to Florida and Montevideo. According to Von 

 Ihering occurring also in the Rio Grande do Sul, but exact localities not known. 



Characters of Shell. — Shell large (length up to 130 mm. and over), moderately 

 and variably soHd, but never thin. Valves distinctly gaping anteriorly, slightly 

 so posteriorly. Outline subtrapezoidal, rather elongated, height 54 to 63 pr. ct. 

 of the length, distinctl}' oblique. Upper margin gently curved or nearly straight, 

 forming a more or less distinct, obtuse angle with the posterior margin, and also 

 with the anterior margin. Sometimes in old specimens these angles are obliterated. 

 Posterior margin obliquely descending, not very steep, straight, or gently convex, 

 curving around into the posterior lower margin, forming a blunt posterior point 

 of the shell, situated a little above the base-line. Lower margin convex, but 

 ascending in its anterior part, and becoming here nearly straight for a distance just 

 in front of the middle; then curving up into the anterior margin. Thus the shell 

 is distinctly narrower anteriorly, and this produc(»s the oblique shape. Often 



