PACIFIC FRESH WATER FISHES. 255 



II. 



THE FISHES OF RIO YAQUI, SONORA, WITH THE DESCRIP- 

 TION OF A NEW GENUS OF SILURIDyE. 



This report is based on two small collections of fishes, 

 one of two species made by Dr. Gustav Eisen at Hermo- 

 sillo, and the other of six species by Mr. William Wight- 

 man Price, in the headwaters of Rio Vaqui, in northern 

 Sonora and southern Arizona. The only collections 

 heretofore reported from Sonora were made in San Ber- 

 nardino Creek by the Mexican Boundary Survey. No 

 species other than those here reported were obtained at 

 that time. 



Dr. Eisen obtained his specimens from a tributary of 

 the Rio Sonora, near Hermosillo*, the capital of Sonora, 

 while in charge of the exploring expedition sent out by 

 the California Academy of Sciences in 1892. He gives 

 the following notes on the stream in question: 



The Sonora River at Hermosillo is a shallow stream, 

 with so little water during the dry season that the stream 

 becomes almost dry. Most of the water is taken out for 

 irrigation above town, leaving the sandy bed dry below. 

 In summer time after heavy rains, however, the water 

 rises quickly and Rio Sonora may then become a torrent 

 of several days' duration. East of Hermosillo the water 

 increases rapidly, and even during the dry season may be 

 several feet deep. The fishes collected were found in 

 pools in the sandy bed, fed by a tiny streamlet in places 

 simply percolating through the sand. 



Mr. Price obtained specimens of fishes in 1894 while 

 collecting birds and mammals in the mountains of south- 

 ern Arizona and northern Sonora. His stations were 

 (1) the Rio Yaqui, east of Oposura; (2) its tributary, San 

 Bernardino Creek, at a point just south of the Arizona 



