242  Salmoperce 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, 
Fic. 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. 
Fic. 193.—Erismatopterus endlichert 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. 
Erismatopteridz.—Here should perhaps be placed the family of 
Erismatopteride, represented by Erismatopterus levatus and other 
species of the Green River Eocene shales. In Erismatopterus the 
