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ing well into the temperate region of North America (Fig. 15), have 

 penetrated Nevada and southeastern and coastal California, where 

 they are represented by 4 genera and 1 1 species. This group is 



Fig. 15. New World distribution of the killifishes, family Cyprino- 

 dontidae, a secondary freshwater group. 



Fig. 16. Railroad Valley springfish, Crenichthys nevadae, a relict 

 confined to warm springs of the enclosed valley (Fig. 15, south central 

 Nevada). Another species lives in a former tributary of the Colorado 

 River and a related genus, Empetrichthys, inhabits the Death Valley 

 system. (From original drawing by Grace Eager; see Hubbs, 1932.) 



