602 MEMOIRS OF THE CARNEGIE MUSEUM. 



Siuipsoii makes Anodonla cciNtclnduiU iluj)e u synonym of Iriyoiia, but 1 do not 

 lliink that this is correct. A. castelnaudi lacks the chi(>f characteristic features of 

 trigona: the pointed posterior end and the rib upon the posterior slope. 



Type-locality. — Rivers of the "province Rio Negro." There is now no such 

 province in Brazil, from which country the collections of 8pix came. 



Other Localities. — Amazonas and Bolivia (Von Ihering, 1893, p. 120); Rio 

 Xingu, Para, Brazil (tributary to lower Amazon) (Von Ihering, 1910, p. 137); 

 Tributaries of Amazon in Bolivia (territory of the Chiquitos and Moxos) (D'Or- 

 bigny); Rio Estacamento, Peru (Haas, 1916); Rio Paraguay, Han Luis de Caceres, 

 JVIatto Grosso, Brazil (Von Ihering, 1915, p. 13); Rio Batel and Rio Parana, Corn- 

 ell tes, Argentina (D'Orbignj). 



New Localities. — Swamp of Lambare, Asuncion, Paraguay (J. D. Haseman 

 coll., March 31, 1909). One right valve. Headwaters of Rio Paraguay, Santa 

 Rita, Matto Grosso, Brazil (J. D. Haseman coll., June 12, 1909). Two specimens, 

 male and female, with soft parts. Rio Limay, Patagonia, Argentina (W. Israel 

 donor). One specimen. 



Distribution. — According to Von Ihering (1890) : " Everywhere in the Amazonas 

 region, but also in the La Plata up to Corrientes." Simpson gives: Brazil, Ecuador, 

 Peru, Bolivia. The species undoubtedly has a wide distribution, both in the 

 Amazon and the Paragua3'-Parana drainages, but is apparently missing in the upper 

 Parana. The new locality in Rio Limay in Patagonia (Rio Negro-drainage) con- 

 siderably extends the southward range. 



Description of Shell. — Shell rather thick and solid. Outline elongated-ovate, 

 pointed behind, lower margin convex, forming a bluntly projecting angle about 

 its middle. Height 59 to 61 pr. ct. of length according to my specimens (in D'Or- 

 bigny's the height is only 54 pr. ct.). Valves not gaping. Dorsal margin gently 

 curved, posterior part almost straight, anterior part descending. Posterior angle 

 of dorsal margin obtuse, but well marked. Anteriorly the dorsal margin forms 

 a very indistinct angle, or passes gradually into the anterior margin. Posterior 

 margin descending obliquely, and almost straight or very gently curved, passing 

 into the posterior part of the lower margin in a very sharp curve, which forms the 

 posterior point of the shell. This point is somewhat elevated above the base- 

 line, since the posterior part of the lower margin slopes upward. This part of 

 the lower margin is almost straight. The lowermost point of the lower margin 

 is a little behind the middle, and in front of it the lower margin changes its direc- 

 tion, running upward and forward, so that this lower point forms a blunt projection. 

 The ascending anterior portion of the lower margin is at first almost straight or 



