294 FISHES OF ILLINOIS 



vigorous growth of algae; and it is worthy of note that the pecu- 

 liar 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 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 inclined 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; vertebra? (B. nigrum) 37 (15 + 22), (B. camurum)38 (17 + 21); py- 

 loric 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, 2V2 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 (Eafinesque) 



johnny darter 

 (Pl., p. 296; Map XC) 



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



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

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



Length 2~y 2 inches; body typically slender, subfusiform, little compressed; 

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

 depth caudal peduncle 2.5 to' 3.3 in its length. Color of back and sides a very 

 pale strawish olive, over which are distributed small brownish dots and 

 splashes and more or less vaguely W-, X-, and V-shaped markings, part of 

 trie latter forming an indefinite lateral row, — rather aptly called "sand- 



