298 FISHES OF ILLINOIS 



It was also impossible to distinguish any correlation, even ap- 

 proximately constant, between robustness of form and scaliness of 

 cheeks and breasts, both stout and slender forms having these parts 

 sometimes naked and sometimes more or less covered with scales. 

 The larger percentage of specimens with scaly breasts and cheeks 

 came from the Rock River basin, from the northwest district, and 

 from the Lake Michigan drainage ; but in all these districts scaly and 

 naked specimens were intermingled, the latter preponderating. In 

 collections from the Kaskaskia, the Saline, the Cache, and the lower 

 Wabash Valley, on the other hand, both cheeks and breasts were 

 almost invariably naked, while in the upper Wabash streams and in 

 the Illinois basin the two forms were indiscriminately commingled. 

 The larger number of the stouter specimens came from the Rock 

 River system and the northwest area, while those from the Kaskaskia , 

 the Cache, and the Saline were of more slender proportions, with the 

 depth usually nearer six times than five times the length. A similar 

 study of specimens from a wider range would probably show that 

 Illinois is in a region of transition between two varieties of this 

 species — the typical nigrum, with slender body and naked breast 

 and cheeks, and some scaly-cheeked variety, probably olmstedi, or 

 perhaps identical with it. 



Fig. 71 



BOLEOSOMA CAMURUM Forbes 



Forbes, 1878, Bull. 111. State Lab. Nat. Hist., II. 2, 40. 



J. & G., 494 (Vaillantia camura and V. chlorosoma) , M. V., 130 (Etheostoma) ; B., 

 I, 96; J. & E., I, 1060; F., 66; L., 27. 



A small species, not reaching more than If inches in length in our col- 

 lections; superficially resembling B. nigrum, but differing distinctly from 

 it in its less angular head and less pointed snout, less protruding eyes, and 

 widely separated dorsals. The small size, the finely and fully scaled 

 cheeks and breast, and the peculiar ring-like light areas on the back be- 

 tween the quadrate dark blotches will usually serve for its recognition. 

 Length If inches; body slender, considerably compressed, greatest width 

 of body about § its greatest depth ; depth 6.5 to 7 . 2 in length ; caudal 

 peduncle slender, its depth 3 . 1 to 3 . 9 in its length. Color much as in 



