THE PCECILIID FISHES OF RIO GRANDE DO SUE AND 

 THE LA PLATA BASIN. 



By Carl H. Eigenmann, 



Of Indiana Unicersity, Bloomingfon, Indiana. 



In a collection of Characins, belonging to the United States National 

 Museum, there were found two specimens of a new Poeciliid from 

 Paraguay. A determination of these made it necessary to look over 

 the entire Poeciliid fauna of the La Plata basin. The results are 

 presented in this paper. 



Von Ihering has pointed out the general similarity between the 

 fresh-water faunas of Rio Grande do Sul and the La Plata basin. The 

 P(eciliids bear out his statement. All species record(>d from Rio 

 Grande do Sul have also been found in the La Plat^a ])asin. and are 

 therefore included in the present paper. 



The Pceciliids, better than any other fresh-water fishes, distinguish 

 the Rio Grande do Sul-La Plata basins as a "province" distinct from 

 the Amazonian on the north. 



An examination of the teeth and male reproductive organs shows 

 that several forms are generically distinct from their northern rela- 

 tives. For instance, Girardinus caudomaculatus Hensel, which 

 Garman^' considers identical with Glaridichthys jarntarius (Hensel), 

 proves to be generically distinct from januarius^ and the latter is shown 

 to be not a Glarid'tchthy.^ but a new genus, unless it is identical with 

 Garman's Cnesterodov, 



The genera may be distinguished as follows (the extra limital rela- 

 tives are in parentheses): 



a. Teeth bicuspid. 



{h. Several series of teeth Characodon.) 



hh. Each jaw with a single series of bicuspid teeth; alimentary canal ;^ times as 

 long as the entire fish. D. 16-18; A. 14 or 15; scales small. Anal of male? 



Ilyodon, 1. 



» The Cyprinodonts, p. 42. 



Proceedings U. S. National Museum, Vol. XXXII— No. 1532. 



425 



