COREGONUS — WHITEFISHES 51 



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

 hind 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 .... 



Cristivomer. 



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 (Artedi) Linn^us 



(WHITEFISHES) 



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

 jecting; lower jaw usually included; premaxillaries broad, with the cut- 

 ting 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 cseca about 

 100; vertebras 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-rakers 11 or 12 on lower limb of first arch; maxillary 4.8 to 5.5 in head, 

 not reaching eye; 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 11. Scales 8-74-9; lateral 

 line continuous. 



