298 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



lVOL. 54. 



(Rutilus) symmetricus} The large series of specimens from the 

 Mohave reveals a considerable degree of differentiation when com- 

 parisons are made with specimens of S. fonnosus and S. obesus, the 

 two species which are geographically nearest them. S. obesus is indig- 

 enous to the Lahontan system and Owens River, The immediate 

 relationship of the Mohave form, which may be known as Siphateles 

 mohavensis, can not be determined with certainty from an examina- 

 tion of the fishes, and unless the geology of the region points to some 

 previous connection between the Mohave basin and the Sacramento- 

 San Joaquin or the Lahontan systems, the question may remain only 

 partly answered. There is reason to doubt the possibility that the 

 species reached the Mohave through stream capture near the head- 

 waters, as the species of Siphateles appear to be lacustrine and channel 

 forms and are not known to migrate far up into the smaller tribu- 

 taries. The occurrence of the genus in streams without deep, slough- 

 like channels or direct connection with a lake is rare, and individuals 

 are not at any time found at a distance from such places. 



Tables intended to illustrate some of the more evident differences 

 which separate S. mohavensis, S. forinosus, and S. obesus, and a de- 

 scription of S. mohavensis follow. 



Description of Siphateles mohavensis, type No. 76837, U.S.N.M., 

 from the Mohave River near Victor, California, August 14, 1915. 

 Clarence H. Kennedy, collector. 



Total length, 149 mm.; length to base of caudal, 122; head, 3.5 in 

 the length; depth, 3.5; depth caudal peduncle, 8; length snout, 3.6 

 n head; diameter eye, 5.2; with interorbital space, 2.9; scales 

 n lateral series, 50; between occiput and dorsal fin, 26; above lateral 

 line, 12; between lateral line and base of ventral, 7. 



» Bull. U. S. Bureau Fisheries, vol. 27, 1907, p. 137. 



