COREGON'US WHITEFISHES 51 



Mouth deeply cleft, the lower jaw articulating with the quadrate bom be 

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

 very small, 175 to 230 in lateral line. 



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. 



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. 



Genius COREGONUS (Artedi) Lixx.eus 



(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 caeca 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. (iill-rakers 11 or 12 on lower limb of first arch; maxillary 4.8 to 5.5 in head, 

 not reaching eve; body long, slender, and roundish, not much elevated or 

 compressed quadrilateralis. 



COREGONUS CLUPEIFORMIS (Mitchill) 



(common whitefish) 



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



i & (', . 299; M. V.. 77; ]. & Iv, I, 465; V. 14 ( Argyrosomus> ; I . 54; F. F., I. 6, 

 95; P., 73; L., 20. 



Length 2 feet or more; body oblong, < (impressed, back always more 

 or less (.]'■ ated, bei oming 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 tn 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 

 I -ii head; lower jaw included; gill-rakers .5 diameter of ryr, usually 

 aboul I0 + l7to 19. Dorsal rays 1 1 ; anal 11 Scales 8 74 9; lateral 

 line continuous. 



