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R. R. MILLER 



are strictly western In distribution ; another, Gila,"^ has only 4 of its 

 approximately 13 species living east of the Continental Divide 

 (Miller and Uyeno, manuscript); 5 {Hybopsis, Hybognathus, No- 

 tropis, Campostoma, and Pimephales) are clearly recent invaders 

 from the East; and one {Rhinichthys) is well represented in both 

 areas, although two-thirds of its species live in the West. The 21 



Fig. 13. New World distribution of the minnow family, Cyprinidae. 

 The extreme northwestern portion of the range is taken from Wynne- 

 Edwards (1952, pp. 18-19). 



genera that are strictly or virtually western may well be autoch- 

 thonous, but it is clear that the family originated in southeastern 

 Asia around the close of the Cretaceous. It has been suggested that 

 there are close relationships between certain western genera and 

 ones that occur in China and Japan — for example, between Mylo- 



* Because of inadequate information about the affinities of this genus, I recognize 

 Gila, Richardsonius (Fig. 14), and Clinostomus as distinct genera, pending further study 

 (see Bailey, 1956, p. 331). 



