FRESHWATER FISH FAUNA 213 



Pleistocene age, between the Bonneville and Lahontan basins. Three 

 of the 4 species (mountain whitefish, cutthroat trout, and Cottus 

 bairdi) shared with the Colorado River are headwater types and 

 indicate headwater transfers from the Bonneville into the Colorado 

 (the fourth species, R. osculus, is too poorly analyzed and too wide- 

 spread to be of much zoogeographic value). 



Lahontan System 



This isolated basin is second in size of the interior drainages and 

 second also in the number and variety of its fishes, with 78 per cent 

 of the primary species endemic (Table II). It has very little of 

 significance in common w^ith the Colorado River (for example, that 

 basin lacks Chasmistes, Siphateles, and Richardsonius , and Gila is 

 absent from the Lahontan basin), but shows afiinities with the 

 Klamath, Columbia, Bonneville, and Death Valley systems. Unlike 

 Lake Bonneville, Lake Lahontan had no outlet in late Pleistocene 

 time and the connections with the surrounding basins were either 

 of comparatively recent headwater exchanges across existing divides 

 (whitefish, trout, and Cottus) or more ancient low-elevation trans- 

 fers, e.g., of Chasmistes (Hubbs and Miller, 1948, p. 40). Black- 

 welder (1948, p. 12) felt that a mid-Pleistocene outlet of the Lahon- 

 tan basin to the sea via Pit River into the Sacramento or into the 

 Klamath, or northward into the Columbia, is a plausible speculation. 



Death Valley System 



This much disrupted drainage is noteworthy for the lack of 

 salmonoids and Cottus, the strength of secondary types (6 out of 10 

 species), and the weakness of the primary fauna (Table II). The 

 highly saline, often warm, and alkaline waters of a large part of the 

 system are particularly suited to the family Cyprinodontidae, of 

 which all the species and 1 of the 2 genera are endemic (Miller, 1948). 

 That this family has been in the system for a long time is attested 

 not only by the high degree of endemism but also by the fossil 

 record (Miller, 1945b) of Cyprinodon and Fundulus from Tertiary 

 deposits in Death Valley. The endemic genus Empetrichthys was 

 probably derived from Fundulus. 



The faunal relationships point to a former connection to the south- 

 east, probably in Pliocene time, with what we now know as the 

 Colorado River, and from the north, with the precursor of Lake 



