GREAT LAKES COREGONIDS 



339 



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 the adjacent rows; gill rakers 15-19, 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 position; lower jaw contained 

 not less than 2.7 times in the head; no vestigial teeth; body subterete; Av/V usually more 

 than 1.9 Prosopium quadrilaterale 



LAKE ERIE 



A. Premaxillaries longer than wide, oblique in position, never retrorse; lower jaw contained not 

 more than 2.3 times in the head; gill rakers long and never less than 40 Genus Leucichthys 



1. L/D usually more than 3.7; Pv/P usually more than 2; Av/V usually more than 1.7; 



lateral-line scales usually more than 79 artedi artedi 



2. L/D usually less than 3.7; Pv/P usually less than 2.1; Av/V usually less than 1.8; 



lateral-line scales usually less than 79 artedi albus 



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

 3.1 times in the head; lower jaw usually contained more than 2.3 times in the head; gill 

 rakers always less than 40 Coregonus clupeaformis 



LAKE ONTARIO (L. NIGRIPINNIS PROGNATHUS EXCEPTED) 



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

 conspicuously smaller than that of those of the adjacent rows; gill rakers more than 23, rela- 

 tively 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 contained 

 not more than 2.3 times in the head; gill rakers relatively long and usually numerous; max- 

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



a. Gill rakers usually less than 41. 



1. Mandible included within the upper jaw; body little compressed laterally; pectorals 



usually contained more than 2.1 times in the pectoral-ventral distance; ventrals 

 usually contained more than 1.4 times in the ventral-anal distance; spring 



spawners reighardi 



aa. Gill rakers usually more than 40. 



b. Body shape in side view usually ovate; fish spawning in summer. 



2. Lateral-line scales usually more than 75; adipose usually contained less than 3.8 times 



in the head; lower jaw usually longer than the upper; ventrals usually contained 



less than 1.5 times in the ventral-anal distance kiyi orientalis 



bb. Body shape in side view usually elliptical; fish spawning in late fall. 



3. Gill rakers seldom more than 47; lateral-line scales seldom more than 76; ventrals 



usually contained less than 1.6 times in the ventral-anal distance; maxillary usually 

 contained less than 2.8 times in the head; mandible usually longer than the upper 

 jaw hoyi 



4. Gill rakers often more than 47; lateral-line scales often more than 76; ventrals usually 



contained more than 1.5 times in-the ventral-anal distance; maxillary usually con- 

 tained more than 2.7 times in the head; mandible seldom longer than the upper 



jaw artedi 



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

 3.1 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 



A A. 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 position; mandible 

 contained not less than 2.7 times in the head; no vestigial teeth; body subterete. 



Prosopium quadrilaterale- 



