436 Illinois State Lnhoratonj of Natural History. 



FAMILY SALMONID^. 



The common lake trout, the white-fish, and the lake her- 

 ring, are the representatives of this great family in the waters 

 of Illinois, and occur there only in Lake Michigan. None 

 of the smaller lakes of the tState contain the herring, or so- 

 called "cisco," as do some of those of Indiana and Wisconsin. 



The food of the trout and adult white-fish having been al- 

 ready studied by the assistants of the United States Fish Com- 

 missioner,* I have given them no special attention.f 



COKEGONUS ARTEDI, LeS. LaKE HeRRING. 



Gills long, deeply arched; gill chamber consequently capa- 

 cious but narrow. Gill-rakers rather long and slender, allowing 

 considerable separation of the gills. Only one row on the 

 anterior arch, about thirty-eight in number, projecting almost 

 directly forward, at least equal in length to the corresponding 

 filaments of the gill. The anterior row on the second gill are 

 as stout as those of the first, but only half as long; the second 

 row represented by about ten triangular rudiments at the lower 

 end of the arch. Anterior row gradually shorter on succeeding 

 gills, posterior row longer; the secon drow on the fourth gill op- 

 posing a similar series on the pharyngeal arch. Each filament 

 with a double row of fine teeth along the inner edge. No phar- 

 yngeal teeth ; pharynx with numerous fine longitudinal ridges 

 which are covered with minute recurved spines. Intestine short 

 and straight, anterior part provided with an immense number of 

 small C(eca. Alimentary canal a little shorter than the head 

 and body without the tail. 



My specimens of this species available for a study of their 

 food were only five in number, obtained at South Chicago in 



small fish ; and a third, five inches in length, had eaten a young cen- 

 trarchid. The two others, respectively two and three fourths and 

 four inches long, had filled themselves with larvie of Agrion and 

 small libellulid larvte. One had taken, in addition, a minute larval 

 Corixa and a small univalve mollusk. 



* See "The Fishery Industries of the United States," pp. 490, 513. 



t For a discussion of the first food of the common white-fish, see 

 Bulletin 111. St. Lab., Nat. Hist., Vol. I., No. 6, pp. 95-109. 



