294 FISHES OF ILLINOIS 



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

 growth of algae; 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 coun^^y 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 algae 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 bo-^tom, 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; vertebras (B. nigrum) 37(15+ 22), (B. camurum) 38 (17+ 21); 

 pyloric cseca 3 to 6; belly with ordinar}^ 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 J 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. 8z G., 402; B., I, 03; J. & E., I, 1056; N., 35 

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



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

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

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



