eigenmann: fresh water fishes. 309 



VI. The Brazilian Region. 



The Brazilian region is divisible into several conspicuously marked 

 provinces ; the Central American, including the area from Veragua to the 

 Isthmus of Tehuantepec; the Pacific, including the Pacific slope from 

 Panama to Peru ; the Amazonian, including all the lowlands drained by 

 the Amazons ; the southeastern, including the streams from Cape San 

 Roque to Santos and the Trinidad Province. Less marked provinces are 

 the La Platan, the Guianan and the Magdalenan, the latter including the 

 Chagres. All of these provinces are distinguished from the Amazonian 

 chiefly by negative characters. The number of peculiar genera varies 

 greatly in the different provinces. 



The question of the character of the different provinces is largely a 

 question of what Amazonian types are absent. We shall take up these 

 provinces in detail emphasizing the Central American, Pacific and Mag- 

 dalenan, as these are of chief interest in discussing later the origin of 

 the Pacific slope fauna, and the East Brazilian and Guianian, because these 

 are the ones principally concerned in the Archiplata-Archhelenis theory. 



Manaos is the centre of the great Brazilian region and the variety of 

 the fauna of any province, other things being equal, varies inversely with 

 its distance from Manaos. The Magdalena' and the San Francisco at 

 opposite sides of Manaos have essentially the same types of fishes. 



I. The Central American Province. 



This province extends from the Isthmus of Darien to the Isthmus of 

 Tehuantepec. 



The most comprehensive account of the Central American province 

 has been given by Giinther (An Account of the Fishes of the States of 

 Central America, Trans. Zool. Soc. VI, 1866). Recently Miller has made a 

 detailed study of the Motagua basin. This province will amply repay 

 further study. ^ Giinther has shown that this province is distinguished 

 from the South American by the absence of most South American fami- 

 lies. A few Pimelodince of the Nematognathi and a few forms of the 

 Tetragonopterinae and of the Characinae are all there is of the one thou- 

 sand species of the Ostariophysias found in the Brazilian region. The 

 genera Cichlasoma and ^Eqnidens are dominant in all the streams. 



' The proof of this had been read before Regan's Pisces of the Biol. Cent. Amer. appeared. 



