FISHES OF COLORADO 107 



groups of animals will prove more interesting to the patient observer, and of the 

 three species recorded from Colorado detailed studies of the particular activities 

 of but one, Boleosoma nigrum, have been made. 



Genus ETHEOSTOMA Rafinesque 

 The Darters 



Etheostoma Rafinesque, Journ. dc Physique, p. 419, 1819. 



Size small, species numerous and variable; distinguished from many of the 

 closely related genera by the non-protractile premaxillaries. 

 Two species of this genus occur in Colorado. 



a. Humeral region with a rather conspicuous black scale or process and a dusky spot; species of 



the Arkansas drainage £• cragini Gilbert 



aa. Humeral region without a black scale or process, although occasionally with a faint dusky spot ; 

 species of the South Platte drainage E. iowae Jordan and Meek 



Etheostoma cragini Gilbert 

 Cragin's Darter (Fig. 52) 



Etheostoma cragini Gilbert, Bull. Washburn College Lab., p. 99, 1885 (tributary of the Arkansas 

 at Garden City, Kansas); Jordan, Bull. U.S. Fish Com., Vol. IX, p. 17, 1889 (pond at Canyon 

 City). 



Body elongate, distinctly compressed back of the pectorals; depth 4.25 to 5 

 in the length to the base of the caudal fin; head rather short, its length 3. 5 to 4 

 in the length of the body; snout short and blunt, 4. 5 to 5 in the length of the head; 

 eye rather large, situated in the anterior half of the head, dorsal margin of the 

 eye on a level with or slightly above the top of the head; diameter of the eye 

 exceeding the length of the snout, 4 or a little more in the head; mouth moderately 

 large, terminal, slightly obHque, angle of the mouth barely reaching the level of 

 the anterior margin of the orbit; premaxillaries not protractile, frenum narrow, 

 about one-half the diameter of the eye; spinous and soft dorsals separate, the soft 

 dorsal being the higher, length of the base about equal to that of the spmous 

 dorsal, spines VII to IX, rays 9 to 11 ; pectorals large, i . 25 to i . 5 in the length of 

 the head; ventrals small; anal short, length of its base less than that of the soft 

 dorsal, of II spines and 6 to 8 rays; scales ctenoid, 6, 45-55, 9 or 10; lateral line 

 interrupted; cheeks naked or rarely with a few scales. 



General color dark olivaceous above, lighter below; scales in the region above 

 the lateral line outlined with dusky, giving that portion of the body a distinctly 

 reticulated pattern; 7 to 10 very poorly defined, dusky blotches on the sides 

 above the lateral line, some of the blotches being so indistinct that they are little 

 more than faint W-shaped marks; a conspicuous dusky bar extending from the 

 middle of the ventral margin of the orbit to the ventral margin of the side of the 

 head, a second less distinct bar of about the same size extending backward from 



