426 



BULLETIN OF THE BUREAU OF FISHERIES 



Pv/P: 



Michigan, (1.5) 1.6-1.8 (2.2). 

 Superior, (1.4) 1.6-1.8 (2.2). 

 Av/V: 



Michigan, 1.2-1.5 (1.6). 

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

 HD+AB 

 M+S 



Michigan, (1.55) 1.75-1.85 (2). 

 Superior, (1.45) 1.65-1.75 (1.85). 

 L/D: 



Michigan, (3.2) 3.4-3.9 (4.3). 

 Superior, (3.2) 3.6-4.3 (4.6). 



Gill rakers on the first branchial arch : 



Michigan, (41) 46-50 (52) .85 



Superior, (36) 38-42 (48). 89 

 Lateral -line scales: 



Michigan, (74) 80-87 (89). 



Superior, (73) 79-86 (91). 

 L/H: 



Michigan, (3.8) 4.1-4.4 (4.7). * 

 Superior, (3.7) 3.9-4.2 (4.4). 

 H/E: 



Michigan, 4-4.4 (4.6). 

 Superior, (4) 4.3-4.6 (5.2). 



H/S: 



Michigan, 3.5-3.9 (4.1). 

 Superior, (3.2) 3.4-3.7 (3.9). 



The most striking differences shown by these figures are the reduction in the num- 

 ber of gill rakers on the first branchial arch, the longer head and snout, the smaller 

 eye, and less body depth in the Lake Superior specimens. In addition, the mandible, 

 which is usually equal to or longer than the upper j aw in the typical form, is as often 

 shorter as equal to the upper jaw and is but seldom decidedly longer. 



This form was described by Jordan and Evermann (1909) as a new species. 

 Their type is a specimen taken off Marquette, Mich. (No. 64672, U. S. National 

 Museum). It is described in most of its characters in Table 45. The reasons for 

 regarding it as a subspecies are discussed on page 331. 



The color in life is less pronounced than in the Lake Michigan form, the colora- 

 tion in general being not very different from that recorded for zenithicus of Superior. 

 Preserved specimens of this race show less pigment, especially on the fins, than pre- 

 served specimens from Lake Michigan. The distal ends of the pectoral rays are paler, 

 and the ventrals are immaculate in over 60 per cent of the specimens collected. Con- 

 centration of pigment in front of the nares is less frequent in the Lake Superior 

 specimens. 



Males and at least some females develop pearl organs in the breeding season. 

 Pearled individuals were collected off Grand Marais, Mich., on October 3, 1917, and 

 off Rossport, Ontario, on October 4, 1921. The development of nuptial excrescences 

 is much like that described for jdhannx on page 350. 



VARIATIONS 



Racial variations. — There are too few specimens from any locality for a study of 

 local variations. The specimens at hand, however, grouped according to locality, 

 do not indicate any marked difference between the groups. 



Size variations. — There is only one specimen smaller than 200 millimeters, so 

 that juveniles can not be compared with adults. Sixty-six specimens 30 centimeters 

 and more in length, when compared with 102 smaller individuals, showed only a 

 somewhat shorter head, smaller eye, greater depth, and shorter paired fins : 



SJ These and other figures for Lake Michigan are based on an examination of 52 specimens ranging in length from 220 to 360 

 millimeters. 



91 These and succeeding figures for Lake Superior are based on an examination of 168 specimens ranging in length from 198 to 

 375 millimeters. 



