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; vertebrae (B. nigrum) 37 (15 -f 22), (B. camurum)3S (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, 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 (EAFINESQUE) 



JOHNNY DARTER 



(PL., p. 296; MAP XC) 



Rafinesque, 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}/ 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 

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



