KEPORT OF STATE BOARD OF FISH COMMISSIONERS. 87 



throat-trout series (allies of Salmo clarHi), the rainbow-trout series 

 (allies of Salmo irideus), and the steelhead series (allies of Salmo 

 gairdneri). 



The steelhead, or (jairdneri, series is found in the coastwise streams 

 of California and in the streams of Oregon and Washington, below the 

 great Shoshone Falls of Snake River, and northward in Alaska along 

 the mainland as far as Skagway. The steelhead trout reaches a large 

 size (10 to 20 pounds). They spend a large part of their life in the sea. 

 In all the true steelheads the head is relatively very short, its length 

 being contained about five times in the distance from tip of snout to base 

 of caudal fin. The scales in the steelhead are always rather small, about 

 150 in a linear series, and there is no red under the throat. The 

 spots on the dorsal fin are fewer in the steelhead (4 to 6 rows) than 

 in the other American trout. 



The rainbow forms are chiefly confined to the streams of California 

 and Oregon. In these the scales are large (about 135 in a lengthwise 

 series), and the head is relatively large, forming nearly one fourth of 

 the length to base of caudal fin. These enter the sea only when in the 

 small coastwise streams and have usually no red under the throat. 



The cutthroat forms are found from Humboldt Bay northward as far 

 as Sitka, in the coastwise streams of northern California, Oregon, Wash- 

 ington, and Alaska, and all the clear streams on both sides of the Rocky 

 Mountains, and in the Great Basin and the headwaters of the Colorado. 

 The cutthroat trout have the scales small, about 180, and there is always 

 a bright dash of orange-red on each side concealed beneath the branches 

 of the lower jaw. 



Along the western slope of the Sierra Nevada there are also forms of 

 trout with the general appearance of rainbow trout and evidently belong- 

 ing to that species, but with scales intermediate in number (in McCloud 

 River), var. shasta, or with scales as small as in the typical cutthroat 

 (Kern River), var. gilherti. In these small-scaled forms more or less red 

 appears below the lower jaw, and they are doubtless what they appear 

 to be, really intermediate between darkii and irideus, although certainly 

 nearest the latter. A similar series of forms occurs in the Columbia 

 basin, the upper Snake being inhabited by darkii and the lower Snake 

 by darkii and gairdneri^ together with a medley of forms apparently 

 intermediate. 



It seems probable that the American trout originated in Asia, extended 

 its range to southeast Alaska, thence southward to the Fraser and Col- 

 umbia, thence to the Yellowstone and the Missouri via Two-Ocean Pass; 

 from the Snake River to the Great Basins of Utah and Nevada; from 

 the Missouri southward to the Platte and the Arkansas, thence from 

 the Platte to the Rio Grande and the Colorado, and then from the Colo- 

 rado again from Oregon southward c Hwise and along the Sierra to 



