Salmonidz 219 
Alaska, and the valley of Mackenzie River have species of 
black-spotted trout. There are few of these north of Sitka in 
Alaska, although black-spotted trout are occasionally taken on 
Kadiak and about Bristol Bay, and none east of the Rocky 
Mountain region. If we are to follow the usage of the names 
“salmon” and “trout”? which prevails in England, we should 
say that, in America, it is only these western regions which 
have any trout at all. Of the number of species (about twenty- 
five in all) which have been indicated by authors, certainly not 
more than about 8 to 10 can possibly be regarded as distinct 
species. The other names are either useless synonyms, or else 
they have been applied to local varieties which pass by degrees 
into the ordinary types. 
The Trout of Western America.—In the western part of America 
are found more than a score of forms of trout of the genus Salmo, 
all closely related and difficult to distinguish.. There are represen- 
tatives in the headwaters of the Rio Grande, Arkansas, South 
Platte, Missouri, and Colorado rivers; also in the Great Salt Lake 
basin, throughout the Columbia basin, in all suitable waters from 
southern California and Chihuahua to Sitka, and even to Bristol 
Bay, similar forms again appearing in Kamchatka and Japan. 
Among the various more or less tangible species that may 
be recognized, three distinct series appear. These have been 
termed the cutthroat-trout series (allies of Salmo clarkit), the 
rainbow-trout series (allies of Salmo irideus), and the steel- 
head series (allies of Salmo rivularis, a species more usually but 
wrongly called Salmo gairdnert). 
The steelhead, or rivularis series, is found in the coastwise 
streams of California and in the streams of Oregon and Washing- 
ton, below the great Shoshone Falls of Snake River, and north- 
ward in Alaska along the mainland as far as Skaguay. The 
steelhead-trout reach a large size (10 to 20 pounds). They 
spend a large part of their life in the sea. In all the true steel- 
heads 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. 
