288 REPORT OP COMMISSIONER OF FISH AND FISHERIES. 



The following - analytical key will enable one to identify with reason- 

 able certainty the various species of whitefishes of America : 



I. Coregonus, the True Whitefishes: 



a. Cleft of mouth short, maxillary and inaudible short; lower jaw not projecting 

 beyond the upper; premaxillaries broad, with the 

 cutting edge nearly vertical or directed backward ; 

 gillrakers on first gill-arch fewer than 30. 

 I>. Gillrakers very short, thickish, about 12 to 16 on the lower limb of the arch; 

 maxillary short and broad, not reaching eve ; mouth 

 very small, 

 c. Maxillary 3| to 4 in head; gillrakers short and thick, 5 to 9+11 to 15; body 

 oblong, the back not elevated. 



d. Scales 60 to 64 in lateral line ; snout blunt and decurved coulterii, 1. 



dd. Scales smaller, 72 to 90 in lateral line. 



e. Supplemental maxillary bone rather narrow ; scales 83 to 90. 

 /. Head moderate, blunt, 4 to 5 in body without caudal ; tip of snout below 

 level of eye; gillrakers 7 to 9+14 or 15, very short; 

 lower fins pale williamsoni, 2. 



ff. Head ^ery short, blunt, 5| in body ; gillrakers short but slender, about 



7+11 ; fins all blackish kennicottl, 3. 



ee. Supplemeutal maxillary bone very broad, semicircular in shape; scales 



72 to 80 riehardsoni, 4. 



cc. Maxillary shorter, 4£ to 51 in head; gillrakers shorter, about 6+11; body 



long, slender, not compressed quadrilateralis, 5. 



bb. Gillrakers more numerous, longer and more slender, 17 to 20 on lower limb of 

 the arch; maxillary longer, about 4 in head, about 

 reaching pupil; mouth larger; preorbital long and 

 narrow. 

 g. Tongue toothless, or nearly so ; back decidedly elevated ; head very 

 low and short, especially in old examples. 

 h. Back elevated, but uot greatly compressed; supplemental maxillary 

 bone nearly twice as long as deep ; head usually 5 to 



51 in length of body clupeiformis, 6. 



hh. Back elevated and greatly compressed; supplemental maxillary 

 bone more thau two-thirds as deep as long ; head about 



5 in length nelsonii, 7. 



gg. Tongue with 3 series of small teeth (not always evident); body 

 elongate, compressed; lower jaw slightly included; 

 head larger; gillrakers 10+15 to 17, about 2 in 

 eye labradoricus, 8. 



II. Argyrosomus, the Lake Herrings : 



aa. Cleft of mouth long, maxillary and mandible long, the former usually extend- 

 ing beyond vertical of pupil; lower jaw long and 

 usually projecting beyond the sharp snout; premax- 

 illaries with the cutting edge nearly horizontal and 

 directed forward ; gillrakers on first gill-arch numer- 

 ous — more than 35. 

 i. Body elongate, herring-shaped; scales small, uniform in shape 

 and size, the free edges convex. 

 j. Lower fins pale or merely tipped with dusky; scales punctate 

 with dark specks. 

 k. Eye large, not much, if any, shorter than snout, its length 

 3£ to 41 in that of head. 



