242 Salmopercs and Other Transitional Groups 



Percopsis guttata, the trout-perch or sand-roller of the Great 

 Lakes, is a pale translucent fish with dark spots, reaching a 

 length of six inches. It abounds in the Great Lakes and their 

 tributaries and is occasionally found in the Delaware, Ohio, 



FIG. 192. Oregon Trout-perch, Columbia transmontana Eigenmann. Umatilla 



River, Oregon. 



Kansas, and other rivers and northwestward as far as Medi- 

 cine Hat on the Saskatchewan. It is easily taken with a hook 

 from the piers at Chicago. 



Columbia transmontana is another little fish of similar type, 

 but rougher and more distinctly perch-like. It is found in 

 sandy or weedy lagoons throughout the lower basin of the 

 Columbia, where it was first noticed by Dr. Eigenmann in 1892. 



FIG. 193. Erismatopterus endlicheri Cope. Green River Eocene. (After Cope.) 



From the point of view of structure and classification, this 

 lett-over form is one of the most remarkable of American fishes. 

 Erismatopteridae. Here should perhaps be placed the family of 

 Erismatopteridtz, represented by Erismatopterus levatus and other 

 species of the Green River Eocene shales. In Erismatopterus the 



