364 



BULLETIN OF THE BUREAU OP FISHERIES 



to its center. The lower jaw is well developed and usually projects beyond the 

 upper. 20 The eye is moderate in size and is contained 4.6 [(3.8) 4.2-4.6 (5.2)] times 

 in the head length. The gill rakers on the first branchial arch number 14 + 25 

 [(11) 13-15 (17) + (20) 22-27 (30) = (33) 36-43 (46)]. 21 



The scales in the lateral line number 75 [(71) 78-85 (96)]. 22 Rows of scales 

 around the body just in front of the dorsal and ventrals number 41 [(40) 41-43 (45)] ; 23 

 just in front of the adipose and the anus 34 [(30) 33-35 (36)]; 24 around the caudal 

 peduncle at its commencement 26 [(23) 24-26 (27)]. 24 Dorsal rays number 10 

 [(9) 10-11)]; 25 anal rays, 11 [(9) 11-12 (13)]; 25 pectoral rays, 16 [(12) 15-17 (18)]; 25 

 ventral rays, 11 [(10) 11 (12)]. 23 The pectorals are Contained 2.2 [(1.6) 1.9-2.2 (2.5)] 

 times into the distance from the pectorals to the ventrals. The dorsal edge of pectoral 

 is usually nearly straight. The length of the ventrals is contained 1.8 [(1.2) 1.4-1.7 

 (1.9)] times in the distance from their origin to that of the anal. 



The color in life is about the same as in johannx. The form is also about as 

 little pigmented, except possibly on the premaxillaries. 



During the breeding season males develop pearl organs, as in the case of other 

 Great Lakes coregonids. No individuals were taken on the spawning grounds, so that 

 no description of the full nuptial dress can be given. Probably the full development 

 of pearl organs is not different from that of the Lake Huron form. 



VARIATIONS 



Racial variations. — Most of the fish in the collection were taken in the northern 

 part of the lake; but probably there are enough specimens from the southern part for 

 comparison. There are no differences discernible between the two groups, however, 

 except that those from the south appear to average still less pigmented on the pre- 

 maxillaries and abdominal fins. 



Size variations. — The usual changes in proportion between the large and small 

 specimens obtain. Ten large and nine small specimens are compared extensively 

 in Table 21. There are only 13 collected specimens less than 200 millimeters in 

 length, and nothing can be stated definitely concerning changes with growth; but it 

 appears that the head, eye, and paired fins are somewhat longer, relatively, in small 

 fish. The depth and width, of course, become greater as the fish approaches maturity. 

 I have seen no sexually mature specimens smaller than 206 millimeters. 



COMPARISONS 26 



Alpenx resembles johannx most closely. The differences between the two spe- 

 cies are discussed on page 351. 



From zenithicus, alpenx differs chiefly in the length of the mandible and maxil- 

 lary, pigmentation of the premaxillaries and maxillary, depth of the head and body, 

 and in maximum size attained. The mandible in alpenx usually is longer than the 



20 In 68 per cent of 638 examined specimens. 



21 Three hundred and eighty-three specimens. 



22 Three hundred and twenty-nine specimens. 



23 Twenty specimens. 

 2< Fifty specimens. 



J s Seventy-five specimens. 



25 Figures for proportions given in this section are based on specimens 200 millimeters or more in length, except artedi, where the 

 1 imit is 225 millimeters. Counts are given for specimens of all sizes. 



