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THE AMERICAN NA TURALIST. [Vol. XXXVI L 



these exceptions belong to other western streams, the other 

 species (Rhinkhthys dulcis) is found in all rivers whose sources 

 are in the Rockies. Of the 18 genera 4 1 are thus far known 

 only from the Colorado basin. 



More than half of the Colorado fishes are minnows (Cyprin- 

 idae), and of these the white salmon (Ptychocheilus lucius Girard ) 



specimens of this species arc occasionally taken which reach a 

 weight of 80 pounds. The blob {Coitus jmnctulatus) is the 

 only spiny-rayed fish known from this basin. 



l"p to within the past year and a half very little was known 

 concerning the fishes of the Rio Yaqui, the largest river in 

 Northwestern Mexico. The few fishes previously taken in that 

 river indicated that its fauna was that of the Colorado. The 

 finding of a bull-head in this basin in 1896 seemed a little 

 strange and it was difficult to account for its presence there. 

 With these facts in mind, when I was collecting fishes in Chi- 

 huahua it was with no small amount of interest that I visited 

 Lago de Castillos which is a part of a small river basin between 

 the head waters of the Rio Conchos and the Rio Yaqui. At 

 Castillos I found only the Rio Grande chub. In the Vaqui I 

 also found this chub, and a number of species I had taken in 



Of 142 species known from the Rio Yaqui, 9 (listed below in 

 bold type) have been taken in the Rio Crande basin, 2< have 

 been found no where else ; one of these ( Gila minaca) belongs 



