6 TRESH-WATER FISHES OF SOUTH AMERICA. — EIGENMANN. 



It will be seeathat all bat two of the tropical Aiuericau families not 

 peculiar to America are fouud iu Africa. 



There is no species of tropical American fishes known to inhabit any 

 other coutiueot, and bat two genera, Osteoglossum and Symbranchus, are 

 found elsewhere. It is a surprising fact that, although there exists the 

 great similarity between the African and the South Americin faunas 

 already pointed out, these two genera are not found in Africa. Sym- 

 branchus inhabits South America and India, Osteoglossum South Amer- 

 ica, Australia, and East Indian Archipelago.* 



We have already called attention to the fact that but one of the South 

 American subfamilies of Silicridte is found elsewhere. The Pimelodince 

 reaches its greatest development in South America (03 species), while 

 in Africa there are but two genera (4 species). 



Of the ten subfamilies of the Gharacinidie four! are euueotropic, three 

 are euafric,| and three § are common to both. 



THE PECULIARITIES OF THE SOUTH AMERICAN FAUNA. || 



As is usual with fresh- water faunas the great majority of South Amer- 

 ican fishes belong to the Physostomous Teleosts. In the words of 

 Wallace: " Richness combined with isolation is the predominant fea- 

 ture of ^Neotropical Zoology, and no other region can approach it in the 

 number of its peculiar family and generic types." 



The families peculiar to South America are: (1) Diplomystidce^ (2) 

 Aspredinidce, (3) Hypophthalmid(e, (4) Fygidiidce, (5) Argiidtv, (G) Lori- 

 cariidcv, (7) Calliehthyidce, (8) Gymnotida', (9) Sternopygidw, (10) Foly- 

 centridw. The first seven belong to the degenerate order i>«ematognathi. 

 The absence of scales, imperfect maxillary, coossified parietals and 

 supraoccipital, the absence of subopercle and coossified anterior verte- 

 brai, distinguish this order. With very few exceptions the species of 

 this order are provided with barbels, which, in some species of Pinie- 

 lodince^ are greatly sj)ecialized, being much longer than the whole fish. 



The Diplomystidce, of which but a single species is known, is undoubt- 

 edly the lowest of the Nematognathi and is a remnant of the primitive 



* Perhaps attention should again be called to the Siluridcv. The genus Tachisurus 

 has representatives in the fresh waters of South America, Africa, and India. It is, 

 however, a marine genus. 



i Erythrinitue, Curimatinw, Jno,'itomatin(e, Serrasalmonince. 



t Cithari)iin(e, Distichodinw, Ichihyoborina'. 



§ Crenuchinw, TetragonopteriiHe, Hijdrocyoninw. 



II Wo wish to call attention to a fact noticed while studying the Nematognathi. 

 The southern representatives of several genera or e ven of the same species have not i ufre- 

 quently more rays than the Amazonian forms. All the specimens of Pseudopiniclodus 

 ewHjraro recorded from the Amazon have six dorsal rays, while three of the specimens 

 from the south have seven dorsal rays. All the Amazonian species of the genus Rham- 

 dia have six dorsal rays, while the southern foruis of the same genus frequently have 

 seven or eight; one peculiar to the La Plata has six to nine, and another conlined to 

 the San Francisco has ten rays. We have not followed this subject in detail and do 

 not know whether the increase in rays is correlated with an increase of vertebrae. 



