GREAT LAKES COREGONIDS 



473 



Gill rakers on the first branchial arch: 



H/M: 



Michigan, (2.3) 2.5-2.6 (2.8)." 

 Ontario, (2.4) 2.5-2.7 (2.8). 38 



Michigan, (37) 41-44 (48) , 33 



Ontario, (39) 42-47 (50) , 34 



Lateral-line scales: 



Michigan, (60) 67-77 (84) , 33 

 Ontario, (63) 67-76 (82) . 3 < 



Pv/P: 



Michigan, (1.6) 1.8-2.1 (2.3). 

 Ontario, (1.4) 1.7-2 (2.2). 



L/H: 



Michigan, (3.9) 4.1-4.3 (4.6). 

 Ontario, (3.8) 4-4.2 (4.6). 



Av/ V.- 

 Michigan, (1.1) 1.3-1.5 (1.7). 

 Ontario, (1.1) 1.3-1.5 (1.6). 



H/E: 



Michigan, (3.8) 3.9-4.1 (4.5). 

 Ontario, (4) 4.1-4.4 (4.7). 



Mandible compared with upper jaw: 

 Michigan, equal 326, longer 726. 

 Ontario, equal 52, longer 199. 



H/S: 



Michigan, (3.5) 3.6-3.9 (4.1). 35 

 Ontario, (3.4) 3.6-3.8 (4.1). 36 



From these data it appears that the Ontario form has, on the average, rather 

 more gill rakers on the first branchial arch, a proportionally smaller eye, and possibly 

 a somewhat longer head and pectorals. The mandible seems to project more often 

 beyond the upper jaw in Ontario specimens. The body of Ontario specimens, on 

 the whole, is also slightly more elongated and more compressed than in the Michigan 

 specimens, especially in the larger ones, which in Michigan often become conspicuously 

 wide. - In other matters, as fin rays, scale rows, etc., the two forms are in virtual 

 agreement. 



The color in life is not conspicuously different from that of the Michigan race, 

 except that pigmentation usually is more extensive and intensive. Alcoholics often 

 show those areas that are most pigmented in the Michigan form (as the entire dorsal 

 surface, the preorbital area, and mandible tip) conspicuously dark, and pigment 

 usually extends farther on the sides, even to below the lateral line. The fins also are 

 darker, except the ventrals, which remain immaculate. The anal more often shows 

 pigment dots on its membranes, and the pectorals always show at least some pigment 

 but usually not more than a lining of black on the dorsal edge. 



The males, at least, develop pearl organs in the breeding season. Only one 

 pearled fish has been collected, and many of the excrescences on it have been removed 

 by friction, but from those remaining I conclude that the development of the breeding 

 adornment probably is not different from that described for the Michigan form. 



Racial variations. — No differences are observable between the groups of speci- 

 mens collected from the various parts of the lake, but it is not improbable that, if 

 sufficient numbers were gathered together, local races might be differentiated. No 

 material is available, either, to determine whether the depth inhabited affects the 

 orm of the body and its parts. 



33 Figures so marked tor Lake Michigan are based on an examination of 1,161 specimens ranging in length from 82 to 265 milli- 

 meters. All undesignated figures are given for 137 individuals ranging between the lengths of 200 and 265 millimeters. 



31 Figures so marked for Lake Ontario are based on an examination of 258 specimens ranging in length from 128 to 277 millimeters. 

 Undesignated figures are given for 236 specimens ranging in length from 200 to 277 millimeters. 



34 Seventy-five specimens. 



38 Two hundred and fifteen specimens. 

 37 One hundred and eight specimens. 



VARIATIONS 



31 One hundred and thirteen specimens. 



