GREAT LAKES COREGONIDS 



385 



H/S: 



Superior, (3.1) 3.3-3.6 (4). 

 Nipigon, (3) 3.2-3.5 (3.8). 

 Pv/P: 



Superior, (1.3) 1.6-2 (2.4). 

 Nipigon, (1.5) 1.6-1.9 (2.1). 

 Av/V: 



Superior, (1) 1.3-1.6 (1.9). 

 Nipigon, (LI) 1.3-1.5 (1.7). 

 L/D: 



Superior, (3.6) 4-4.7 (5.1). 

 Nipigon, (3.5) 3.7-4.5 (5). 



Leucichthys zenithicus of Lake Nipigon 



Zenithicus of Lake Nipigon is compared in the chief characters with the typical 

 race below: 



■Gill rakers on the first branchial arch: 



Superior, (34) 39-43 (46) , 37 



Nipigon, (33) 36-39 (42) 

 Scales in lateral line: 



Superior, (69) 74-84 (90). 



Nipigon, (66) 70-77 (83). 

 L/H: 



Superior, (3.6) 3.8-4.1 (4.4). 

 Nipigon, (3.5) 3.7-4 (4.2). 

 H/E: 



Superior, (3.9) 4.2-4.6 (5.1). 

 Nipigon, (3.6) 4-4.4 (4.6). 

 H/M: 



Superior, (2.1) 2.3-2.5 (2.7). 

 Nipigon, (2.2) 2.3-2.5 (2.8). 



The comparisons show that the Nipigon race differs from the typical race in 

 having fewer gill rakers and lateral-line scales and possibly a relatively larger head, 

 eye, and snout, and a slightly deeper body. It has also fewer scale rows. 



The color in life is much paler than in the typical race. The pea green of the 

 back is very pale, and the green cranial patches are often wanting. Pigmentation 

 also is reduced, especially on the dorsal surface and on the maxillary, which usually 

 is pigmented over not more than one-fourth its area, and on the abdominal fins, 

 which are usually immaculate. 



No pearled individuals have been seen, but pearl organs doubtless are developed 

 during the breeding season. 



VARIATIONS 



Racial variations. — The examination of my specimens shows no indication of 

 the occurrence of well-marked races in the lake. There are not enough specimens 

 available for extensive comparison, however. 



Size variations. — In Table 27, 10 specimens more than 200 millimeters long and 

 10 less than 200 millimeters long are compared extensively. The differences between 

 the two groups are of proportion. Small specimens have a relatively larger head 

 and eye, longer paired fins, a relatively somewhat shorter snout and maxillary, and 

 less body depth. 



Of the 14 small specimens examined, none were found sexually mature at less than 

 170 millimeters. 



comparisons 39 



Zenithicus is separable from all the species of Leucichthys of the lake except 

 reighardi and hoyi by the number of gill rakers on the first branchial arch, which in 

 none of the other forms number less than 44 and in zenithicus not more than 42. 



> 7 These and succeeding figures, except those for lateral-line scales, are based on an examination of 787 specimens ranging in 

 length from 200 to 332 millimeters. Those for scales are given for 956 specimens. 



!8 Figures for gill rakers and lateral-line scales are based on an examination of 160 and 147 specimens, respectively. All others 

 are given from an examination of 141 specimens ranging in length between 200 and 308 millimeters. 



" The specimens compared for proportions are those 200 millimeters or more in length or, in the case of artedi, 225 millimeters 

 or more. The counts are given for specimens of all sizes. 



