336 



BULLETIN OF THE BUREAU OF FISHERIES 



BB. Premaxillaries wider than long, retrorse in position; maxillary usually contained not less 

 than 3 times in the head, but less than 3.8; lower jaw usually contained 2.4-2.7 times in 



the head; gill rakers less than 32 and more than 20 Coregonus clupeaformis 



AA. A single flap between the openings of a nostril; exposed area of the scales of the lateral line 

 conspicuously smaller than that of those of adjacent rows; gill rakers less than 20, the 

 length of the longest not more than 5 per cent of the head; maxillary usually contained 

 more than 3.8 times in the head; premaxillaries wider than long, retrorse in posi- 

 tion; mandible contained not less than 2.7 times in the head; no vestigial teeth; body 

 subterete Prosopium quadrilaterale 



LAKE SUPERIOR 



A. Two flaps between the openings of a nostril; exposed area of the scales of the lateral line not 

 conspicuously smaller than that of the adjacent rows; gill rakers more than 23, relatively 

 long and slender; maxillary usually contained less than 3.8 times in the head; vestigial teeth 

 usually present on the premaxillaries, palatines, mandible, and tongue; body usually laterally 

 compressed. 



B. Premaxillaries longer than wide, usually oblique in position, never retrorse; mandible con- 

 tained not more than 2.3 times in head; gill rakers relatively long and usually numerous; 



maxillary seldom contained more than 3.1 times in the head Genus Leucichthys 



a. Lower jaw usually longer than the upper and more or less hooked; fish seldom longer than 

 than 200 millimeter (7J4 inches) ; body usually conspicuously bloated. 



1. Body shape in side view ovate; gill rakers usually less than 41; lateral-line scales 



usually more than 75; pectorals usually contained less than 1.6 times in the 

 pectoral-ventral distance kiyi 



2. Body shape in side view elliptical; gill rakers usually more than 40; lateral-line 



scales usually less than 76; pectorals usually contained more than 1.5 times in the 



» pectoral-ventral distance hoyi 



aa. Lower jaw usually equal to or shorter than the upper, seldom conspicuously longer and 

 hooked; fish attaining length of 300 millimeters or more (12% inches). 

 b. Gill rakers usually more than 43. 



3. Lateral-line scales seldom less than 80; pectorals seldom contained less than 2 times 



in the pectoral-ventral distance; ventrals seldom contained less than 1.6 times in 

 the ventral-anal distance; head in adults usually contained 4.3-4.6 times in the 

 total length; maxillary usually contained 2.7-3 times in the head; body sub- 

 terete artedi artedi 



4. All figures given above tend to be less and the body deeper and more compressed 



in artedi albus 



bb. Gill rakers usually not more than 43. 



c. Body shape ovate in side view; fish spawning in September. 



5. Sum of the head depth and the anal base divided by the sum of the maxillary and 



the snout usually 1.65-1.75; body usually deeper than under cc; mandible tip 



usually conspicuously pigmented nigripinnis cyanopterus 



cc. Body shape elliptical in side view; fish spawning in November or later; lower jaw 

 usually shorter than the upper; mandible usually immaculate or faintly pigmented. 



6. Gill rakers usually less than 39; snout usually contained 3.6-3.9 times in the head; 



eye in adults usually contained 3.9-4.2 times in the head; length of the pectoral 

 fin usually contained 1 . 8-2 times in the pectoral-ventral distance _ - reighardi dymondi 



7. Gill rakers usually not less than 39; snout usually contained 3.3-3.6 times in the 



head; eye in adults usually contained 4.2-4.6 times in the head; the sum of the 

 head depth and anal base divided by the sum of the maxillary and snout usually 



1.45-1.55 zenithicus 



BB. Premaxillaries wider than long, retrorse in position; maxillary usually contained more than 

 3.1 but less than 3.8 times in the head length; mandible usually contained 2.4—2.7 times 

 in the head; gill rakers 24-31; ventrals usually contained less than 1.9 times in the ven- 

 tral-anal distance Coregonus clupeaformis 



