204 Bass, Pike, and Percb 



Coregonus ivillianisotti cis-monianus. Montana Whitefish. Head 5 ; 

 depth 5 to 5^; pectoral fin i^ in head; ventral i^; scales 90. 

 Otherwise like the t3-pical form. 



Argyrosomus ariedi sisco. Cisco. Head 4 to 5 ; depth 4 to 4J; 

 eye 4 to 5 ; D. 10 ; A. 12 ; scales 8-65 to 80-8; body long, 

 slender and somewhat compressed ; head long, pointed and com- 

 pressed ; mouth large, lower jaw somewhat projecting, ma.xillary 

 reaching to pupil ; mandible 2|- in head ; dorsal fin high, its 

 rays rapidly shortened ; caudal fin forked. 



THE ROCKY MOUNTAIN WHITEFISH 



{Coregonus williamsoni) 



This fine fish was first described from the Des 

 Chutes River in Oregon by Dr. Charles Girard 

 in 1856, who described most of the fishes col- 

 lected during the Pacific Railroad Survey, and 

 named the one under consideration in honor of 

 Lieutenant R. S. Williamson, who had charge of 

 one of the divisions of the Survey. 



Its general form is not unlike that of the gray- 

 ling, which has led to the absurd opinion, held by 

 some, that the grayling is a hybrid, or cross, be- 

 tween this whitefish and the red-throat trout, its 

 body being rather long, nearly elliptical in outline, 

 and somewhat compressed. It is found in the 

 clear streams on both slopes of the Rocky Moun- 

 tains, and on both sides of the Cascade Range. In 

 the tributaries of the Missouri River in Montana 

 it differs slightly from the typical form, and is 



