DISTRIBUTION OF THE FISHES 65 
spoken of as mountain genera, they pertain to the fauna of the rapid rivers of the 
tropical rain forest, elevations of a few hundred feet to 5000 or 6000. 
Prior to the National Geographic Society’s collections and our own the follow- 
ing fishes had been listed from the upper and Middle Urubamba: 
Hypostomus bufonius and calamita by Cuvier and Valenciennes 
Astroblepus sabalo - et vi 
Pygidium incae 
gracilis 
Orestias owenit 
ue eUUSSVED 
agassizi1 
pentlandi fuscus 
Astroblepus sabalo 
Pygidium dispar 
Acrobrycon ipanquianus 
ce 
Garman 
Cope 
a3 “ 
is 
The distribution of the mountain fishes by genera rather than by species may 
be more graphic and illuminating: 
Astroblepus Andes Urubamba to Panama and Mérida 3800-13400 feet 
Ancistrus Rio Chagres to Guiana and Buenos Aires up to 9000 feet 
Pygidium mountains Punta Arenas to Panama 0—-14000 feet 
Pimelodella Panama to Buenos Aires 0—6000 feet 
Bryconamericus Costa Rica to Buenos Aires 0—4000 feet 
Acrobrycon Eastern slopes Bolivia, Peru 4000-8000 feet 
Hemibrycon Urubamba to Panama and Trinidad 0-11500 feet 
Creagrutus s “i = * Guianas 0-4000 feet 
Ceratobranchia Southern Peru to Chanchomayo 2000-3500 feet 
Astyanax Texas to Buenos Aires 0—3500 feet 
Orestias Mantaro to northern Chile 9000-15000 feet 
Steinmann (as quoted in Eigenmann, 1909, III, 372) holds that as late as the 
Tertiary the Titicaca basin was a body of water or a deep valley draining normally 
southeastward to the southern tributaries of the Amazon. The rapid rise of the 
Eastern Cordillera interrupted its outlet, creating its closed system of drainage. 
Looking at the topography from the pampa above the La Paz gorge, you would 
be inclined to take that view of it, although an equally alluring solution is presented 
south of Uyuni by the intercordilleran valley now closed by volcanic action. For 
the following reasons I should prefer to regard the Titicaca basin as a closed one 
for a much longer period. 
Prior to the extreme present elevation of the Eastern Cordillera the interior 
valley should have had much greater rainfall, as the lower eastern ranges of the 
time would have been less effectual in cutting off the southeastern trade-winds. If 
an open way to the Atlantic existed then along the path of the moisture-laden winds, 
it would have been kept open. Northward of this, the present valleys of the 
Urubamba, Apurimac, etc., have maintained an outlet despite the rise of high 
