388 BULLETIN OF THE BUREAU OF FISHERIES 



Leucichthys zenithicus of Lake Michigan 



The zenithicus of Lake Michigan resembles closely the typical form in respect 

 to body shape, adult size, and most systematic characters. The chief characters are 

 compared below: 



Gill rakers on the first branchial arch: 

 Superior, (32) 39-43 (46). 40 

 Michigan, (35) 38-42 (44)." 



Scales in lateral line: 



Superior, (69) 74-84 (90) .« 

 Michigan, (70) 75-85 (91) « 



L/H: 



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

 Michigan, (3.9) 4-4.3 (4.5). 

 H/E: 



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

 Michigan, (4) 4.2-4.5 (5). 



H/M: 



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

 Michigan, (2.2) 2.4-2.6 (2.8). 



H/S: 



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

 Michigan, (3.2) 3.4-3.7 (4). 

 Pv/P: 



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

 Michigan, (1.7) 2-2.2 (2.6). 

 Av/V: 



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

 Michigan, (1.2) 1.4-1.6 (2). 



These data indicate that the Michigan form has a shorter head and pectorals 

 than the typical form. The snout, maxillary, and ventrals may also be somewhat 

 shorter, and the body, on the average, is somewhat wider. It is noteworthy, also, 

 that while in Lake Superior zenithicus almost invariably has pigment on the maxillary, 

 176 out of 487, or about one-third, of the individuals examined of the form in Lake 

 Michigan have no pigment except occasionally on the jugal. The premaxillaries 

 in the latter class are also immaculate or but lightly pigmented, and the mandible 

 more often is included within the upper jaw. 



The color in life is not strikingly different from that of the typical form except 

 for the reduced pigmentation. The dorsal surface and the fins are conspicuously 

 less pigmented than in the Superior form, and of the fins the anal and ventrals are 

 often immaculate. 



Males, at least, develop pearl organs during the breeding season. The breeding 

 dress is not known to be different from that described for johannx, on page 350. 



VAKIATIONS 



There are too few specimens from any locality to indicate whether there is 

 local variation in this species. Small individuals of the species, however, as is usual, 

 differ in certain characters from larger ones. In Table 29 are presented a series of 

 counts and proportions for 7 specimens smaller than 200 millimeters, and for 10 larger 

 than 200 millimeters. It appears from this table that the head, eye, and paired fins 

 are somewhat larger in the smaU specimens and the maxillary relatively somewhat 

 shorter. 



Only one of these small specimens (a male, 192 millimeters) shows sex organs 

 approaching maturity. Of two other small fish collected, but not recorded in the 

 table, one male (165 millimeters) is mature. 



« Eight hundred and eighty-three specimens 



« These and other figures for Lake Michigan, unless otherwise marked, are based on an examination of 123 specimens, ranging 

 in length from 200 to 312 millimeters. 



« Nine hundred and fifty-six specimens. 

 13 One hundred and forty specimens. 



a These and other figures for Lake Superior, unless otherwise marked, are based on an examination of' 787 specimens, ranging- 

 in length from 200 to 332 millimeters. 



