eigenmann: fresh water fishes. 305 



« 



M Chiyostoma lermce Boulenger. 



M Chirostotna ocotlance Jordan & Snyder. 



M Chiro stoma ^5/19^ Jordan. 



CT Agoiiostomiis mouticola (Bancroft). 



CS Cichlasouia beam' (Jordan). 



It is evident "from a glance at the letters showing the relationship of 

 these species that the Mexican fauna has not been influenced by the South 

 American fauna. Nor has it influenced in any way the South American 



fauna. 



V. The Andean Region. 



The Andean Region includes the high Andes on both slopes from 

 Venezuela and Colombia to Chili. 



It is poor in species at any given point, but some of the genera have a 

 large number of local adaptations or species. This region is distinctly 

 marked off into three provinces. 



1. The Northern includes the high lands of northern Peru, Ecuador, 

 Colombia and Venezuela. This is the richest in species and distinguished 

 by the genera Arges, Cyclopiuni, Prenadilla and the high development of 

 Chcetostomus. Its fauna is largely an ancient derivative from the low- 

 land fresh-water fauna of Archiguiana^ 



2. The Titicacan, including the basin of Titicaca and neighboring 

 streams, and possibly the land-locked basins of Bolivia, concerning which 

 nothing is known, is distinguished by the genus Orestias and the absence 

 of the genera distinguishing the Northern province. Its fauna is largely 

 an ancient derivative from the ocean. 



3. The Southern is the poorest in species, characterized by the absence 

 of everything but a few species of Pygidium, a genus which extends the 

 entire length of the Andean Region. 



Concerning the physical features of the Titicacan province Agassiz 

 says (Bull. Mus. Comp. Zool. Ill, No. 11, 1875): 



" In fact, the geography of the whole of the west coast of the Andes to 

 the north of Chili seems to point to a former condition of things such as 

 we now find on the west coast of Chili. The plains to the southward of 

 Santiago, bounded by the coast range to the westward, and the Andes to 

 the east, gradually pass to the condition of the coast now prevailing at 

 Conception Bay, and south of it — the coast range forming the archipel- 

 ago, the Andes forming the coast range, and the plains of the more 



