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Indiana University Studies 



A comparison of the faunas of the Upper Cauca, the Dagua r 

 and the Patia rivers, to determine to what extent the Cauca con- 

 tributed to the Pacific slope Dagua and Patia and these to each 

 other, shows that the Cauca's contribution over the Cordillera 

 Occidental is all but nil. 



There is but one species common to the three rivers, Brycon 

 henni, which is not also found in the Atrato. 



One mountain form, Pygidium chapmani, is common to the 

 Upper Cauca and the upper course of the Dagua. Four high 

 mountain species, AstroMepus grixalvii, A. chotae, Brycon- 

 americus caucanus, and Remibrycon tolimae, are common to the 

 Cauca and the Patia. (See p. 13, lines 27 to 31.) 



The fauna of the Patia consists of several Ecological groups. 



I. High Andean forms: Pygidium taenium, AstroMepus grixalvii and 

 chotae, Bryconamericus caucanus, Hemibrycon tolimae. All but the first 

 of these are also found in the Cauca, and all but the last two are also 

 found south of the Upper Patia. 



II. Lowland species of remote marine origin : Tylosurus fluviatilis, 

 Thyrina colomMensis , Pornadasys and the members of the Gobiidae. All 

 of these, except possibly Thyrina colombiensis, are found both north and 

 south of the Patia. 



III. Twenty-five strictly fresh-water fishes living somewhere between 

 brackish water and 3.000 feet. Of these : 



a. One has a wide distribution both north and south of the Patia : 

 Sternopygus macrurus. It may have come from the south or the north. 



I). Other species and varieties : Bryconamericus guaitarae, Curimatus 

 lineopunctatus patiae, and Chaetostomus leucomelas are peculiar to the 

 Patia. They are modifications of San Juan-Atrato species. 



c. Hemimicistrns amnectens and Cichlasoma ornatum are all but con- 

 fined to the Patia, being found elsewhere only in northwestern Ecuador. 



d. The remaining species, 68 per cent of the 25 strictly fresh-water 

 species, are found in one or all of the rivers Dagua, San Juan, Atrato to 

 the north. A few of them, Pseiidopimelodus transmontanus, Pimelodella 

 grisea, Loricaria jubata, and Brycon oUgolepis. found in the north extend 

 a few miles south of the Patia into northwestern Ecuador. 



Twenty-two species, 62 per cent of the entire Patia fish fauna, 

 are known to occur in the Atrato, the San Juan, or the Dagua. 



A certain per cent of the fauna of any river will be found in 

 the rivers to either side of it. The very large per cent of the 

 Patia fishes also found in the Atrato-San Juan, compared with 

 a much smaller per cent found in the nearer Guayas, indicates 

 beyond any peradventure that faunally the Patia belongs to the 

 group of rivers to the north of it. 



