FISHES, LAHONTAN SYSTEM OF NEVADA AND NORTHEASTERN CALIFORNIA. 6 1 



appear to possess some characters that are in a degree more or less distinctive." The same is true of 

 S. obesus, although apparently to a lesser extent. From S. columbianus, S. bicolor, and S. formosus 

 the species in hand differs in having smaller scales, as illustrated by the following tables: 



The same genus is represented in Owens River and also in the Mohave River. Owens River speci- 

 mens are very similar to those of S. obesus from the Lahontan system, while those from the Mohave seem 

 to differ from all the others. Sufficient material for careful comparisons is not now available however. 



S. obesus is both lacustrine and fluvial, reaching its maximum size and abundance in lakes and 

 deep ponds, thriving in the lower courses of the rivers, but apparently not entering the swifter, clearer, 

 and more shallow upper courses and tributaries. It is distributed almost universally throughout the 

 Lahontan system, being like S. oregonensis, a species that maintains itself to the last in a dessicating 

 basin. 



S. obesus is a minnow with a large, robust body, large head, and relatively short fins. With ad- 

 vancing age and increasing size the head grows larger and the snout longer in relation to the body. Often 

 a pronounced hump appears on the back behind the head. This hump is decidedly more prominent 

 in alcoholic specimens than in life, however. Some individual difference appears in the depth of body, 

 size of eye, height and length of fins, etc., but this is not found to be coordinate with locality, i. e., dis- 

 tinct basins, except that specimens from the Humboldt River and its tributaries seem to represent the 

 extreme of large bodies and short, rounded fins. 



There are from 50 to 60 scales in the lateral line, usually 53 to 56; 27 to 33 before the dorsal, usually 

 29 to 31 ; 12 to 16 before the lateral line. There are 8 rays in the dorsal fin and 7 or 8 in the anal. The 

 number of scales and dorsal and anal rays aid in distinguishing between this and allied species: 



An inspection of this table might lead to the supposition that well-defined local races, perhaps subspecies in the commonly 

 accepted meaning of the term, might here be recognized. But investigation along that line shows that these races, if they may 

 be so termed, are not of apparent geographical or distributional significance. 



o Bulletin. Bureau Fisheries, vol. xxvn, 1907, p. 87-93. The characters referred to are seen in body proportions, length of 

 fins, etc. One illustration will suffice. 



69571°— 18 5 



