294 FISHES OF ILLINOIS 



.swift water, oftenest on rocky ripples where there is a vigorous 

 growth of alga;; and it is worthy of note that the peculiar color 

 of this fish seems to assimilate it to its surroundings. 



Specimens taken from the Vermilion in Vermilion county were 

 kept by us for several weeks alive in a soft-water aquarium aerated 

 by compressed air. They were very shy and easily frightened, and fell 

 into a panic when disturbed by a sudden movement in the room or 

 by a jar of the aquarium, their actions when frightened — too quick 

 for the eye to follow — stirring up the sand and gravel on the bottom 

 and so clouding the water as to hide their retreat. They seemed 

 very much attached to a mass of algas placed in the aquarium with 

 them, lying in it by the hour, and they were frequently seen perched 

 on a pebble or stone by means of their ventrals, with the body in- 

 clined at an angle of 30 to 45 degrees. When on the bottom, the 

 body was usually curved in a snake-like position, as if prepared for a 

 quick and vigorous stroke. 



Genus BOLEOSOMA De Kay 



(tessellated darters) 



Body moderately elongate, subcylindrical;but slightly translucent; 

 mouth small, horizontal, subinferior; premaxillaries protractile; teeth 

 on vomer; vertebrae (B. nigrum) 37(15+ 22), (B. camurum) 38 (17+ 21); 

 pyloric caeca 3 to 6 ; belly with ordinary scales; plainly colored, usually 

 olivaceous with black or brown specks and with no red or blue; spring 

 males dusky to jet-black. Size small, 2\ inches; species about 5. 



Key to Species of BOLEOSOMA found in- Illinois 



a. Lateral line complete or nearly so; pyloric caeca 6; cheeks and breast typic- 

 ally naked, sometimes more or less scaly • nigrum. 



aa. Lateral line absent on posterior half of body; pyloric caeca 3; cheeks and 

 opercles, and usually breast, closely scaled camurum. 



BOLEOSOMA NIGRUM (Rafinesque) 

 (johnny darter) 



Rafinesque, 1820, Ichth. Oh., 37 (Etheostoma). 



G., I, 77 (Boleosma maculatum) ; J. & G., 492; B., 1, 93; J. & E., I, 1056; N., 35 

 (brevipinne and olmstedi) ; j., 40 (maculatum and olmstedi); F., 66; L., 27. 



Length 2\ inches; body typically slender, subfusiform, little com- 

 pressed; depth 4.7 to 6.9 in length; greatest width of body about J its 

 greatest depth ; depth caudal peduncle 2 . 5 to 3 . 3 in its length. Color 



