COREGONUS WHITEFISHES 51 



aa. Mouth deeply cleft, the lower jaw articulating with the quadrate bone behind 

 the eyes; strong- teeth on jaws, vomer, palatines, and tongue; scales very 

 small, 175 to 230 in lateral line. 

 c. Vomer with a raised crest, extending backward from the head of the bone, free 

 from its shaft, and armed with strong teeth; hyoid bone with a broad band of 

 strong teeth; species grayish-spotted, without bright colors Cristi vomer. 



cc. Vomer without raised crest, only the head being toothed; hyoid bone with 

 very weak teeth or none; species red-spotted, the lower fins with bright 

 edgings Salvelinus. 



Genus COREGONUS (Aetedi) Linn^us 



WHITEFISHES 



Body more or less elongate, compressed; head conic, the snouth pro- 

 jecting; lower jaw usually included; premaxillaries broad, with the cutting 

 edge nearly vertical; jaws toothless or nearly so; gill-rakers usually rather 

 short; dorsal fin about median, of 11 to 14 rays; caudal deeply forked; scales 

 thin, cycloid; air-bladder very large; pyloric caeca about 100; vertebrae 56 

 to 60. Clear lakes of northern Europe, Asia, and America. Species about 

 15, of which 3 are found in the Great Lake region. 



Key to Species of COREGONUS found in Lake Michigan 



a. Gill-rakers 17 to 20 on lower limb of first arch; maxillary about 4 in head, 

 about reaching pupil; body considerably compressed, the back arched in 



front of dorsal fin clupeiformis. 



aa. Gill-rakex-s 11 or 12 on lower limb of first arch; maxillary 4.8 to 5.5 in head, 

 not reaching ej'e; body long, slender, and roundish, not much elevated or 

 compressed quadrilateralis. 



COREGONUS CLUPEIFORMIS (Mitchill) 



COMMON WHITEFISH 



Mitchill, Amer. Month. Mag., II, 1818, 321 (Salmo). 



J. & G., 299; M. V., 77; J. & E., I, 465; N., 44 (Argyrosomus) ; J., 54; F. F., I. 6, 95; 

 F., 73; L., 20. 



Length 2 feet or more; body oblong, compressed, back always more 

 or less elevated, becoming notably so in the adult; depth in length 3 to 4. 

 Color olivaceous above; sides white, not silvery; lower fins sometimes dusky. 

 Head 5, comparatively small and short; interorbital space 3.4 in head; eye 

 4 to 5; nose 3.8 in head; tip of snout on level of lower edge of pupil; mouth 

 small, maxillary reaching past front of orbit, about 4 in head; lower jaw 

 included; gill-rakers .5 diameter of eye, usually about 10-|-17 to 19. Dorsal 

 rays 11; anal IL Scales 8-74-9; lateral fine continuous. 



This is a northern species, occurring in vast abundance in 

 all the Great Lakes and in some of their tributary waters, and 

 ranging north to the Arctic Ocean. It was formerly abundant 

 in southwestern Lake Michigan within the limits of the State of 



