; The Yellowstone Trout 



of side usually with a diffuse pale rosy wash, this sometimes 

 quite bright, and extending on to side of head; under parts silvery 

 white. The red blotches or washing on the membrane joining 

 the dentary bones of the lower jaw are usually constant, prob- 

 ably always present in the adult, and constitute a most important 

 character. 



This species has been called Salmo mykiss in various publi- 

 cations by the writers and others, but the true Salmo mykiss is 

 allied to Salmo salar, and has never been taken outside of 

 Kamchatka. 



Yellowstone Trout 



Salmo lewisi (Girard) 



The Yellowstone or Lewis trout inhabits the Snake River basin 

 above Shoshone Falls, and the headwaters of the Missouri. It is 

 abundant throughout this whole region in all accessible waters, 

 and is particularly numerous in Yellowstone Lake. As already 

 stated the trout of Yellowstone Lake certainly came ^into the 

 Missouri basin by way of Two-Ocean Pass from the Upper Snake 

 River basin. One of the present writers has caught them in the 

 very act of going over Two- Ocean Pass from Pacific into Atlantic 

 drainage. The trout on the two sides of the pass cannot be 

 separated, and constitute a single species. 



Silver Trout 



Salmo gibbsii Suckley 



In the tributaries of the Columbia, between Shoshone Falls 

 and the Cascades, in the lakes and larger streams, there is a trout 

 which may be called the silver trout. It is particularly common 

 in the Des Chutes River, and in the Payette Lakes in Idaho. 

 Examples about 15 inches long taken in Big Payette Lake, Septem- 

 ber 27, had the spots small, half circles, few below middle of side; 

 rosy wash on side and opercles, brightest in the male; scarcely 

 any red on throat; belly silvery, back dark-greenish; scales about 140 

 to 145. On this date, while sailing across this lake, trout could be 



179 



