GREAT LAKES COREGONIDS 



479 



and as all, including the long, slender, blue-backed type (the cisco huronius of Jordan 

 and Evermann), may be taken in the same spawning school, the various types can 

 not be considered more than races. The satisfactory differentiation of these races 

 still remains to be made. The depth of the body is very variable and ranges between 

 the limits of (2.8) 3.3-3.7 (4.8), 42 the figures being highest in the "blueback" or 

 typical artedi. The width of the body also is variable. In the alius form it comprises 

 about 49 or 50 per cent of the depth but in typical artedi may be more than 60 per 

 cent. The head is more or less compressed, broadly triangular in side view, and is 

 contained (4.1) 4.3-4.7 (5.2) times in the total length. Its dorsal profile is more or 

 less convex. The premaxillaries are always pigmented and are very short, scarely 

 longer than wide; they usually make an angle of 45° to 55° with the horizontal 

 axis of the head. The snout is obtuse in side view, short, sometimes equal to or 

 shorter than the eye, never much longer, and is contained (3.6) 3.8-4 (4.5) times 

 in the head length. The eye is relatively small, is usually situated in the second 

 quarter of the head length (though often in the smallest specimens encroaching 

 on the third), and is contained (3.8) 4.2-4.5 (4.9) times in the head length. The 

 maxillary is always pigmented except on its distal end, is short, and is contained 

 (2.5) 2.7-2.9 (3.3) times in the head. The mandible is also always pigmented, is 

 rather weak, and is usually equal to or shorter than the upper jaw, though often 

 somewhat longer. The gill rakers on the first branchial arch number (15) 16-18 

 (20) + (26) 28-31 (33) = (41) 44-48 (53). 43 The scales in the lateral line number 

 (64) 71-81 (89), 44 their number directly influencing the size of the body scales. 

 Scale rows 45 around the body just in front of the dorsal and ventrals number (38) 

 40-42 (46), just in front of the adipose and anus (31) 32-34 (36), around the caudal 

 peduncle at its commencement (23) 24-25 (27). The paired fins are short. The 

 pectorals are contained (1.6) 1.9-2.1 (2.5) times in the distance from their insertion 

 to that of the ventrals, and the ventrals are contained (1.4) 1.6-1.8 (2.1) times in 

 the distance from their insertion to that of the anal. There are (8) 9-1 1 45 dorsal rays, 

 10-12 (13) 45 anal rays, (10) 11 (12) 45 ventral rays, and (14) 15-16 (18) 45 pectoral rays. 



The general appearance in life is silvery, with a faint pinkish to purplish irides- 

 cence on the sides. The underlying color on the back is blue green to pea green of 

 moderate intensity, except in the case of the "blueback," which is usually deep 

 blue green. This color extends on the sides about halfway to the lateral fine and 

 then pales gradually to the colorless belly, becoming more bluish below the lateral 

 line. The cranial and preorbital patches are present and vary in color like the back. 

 The effect of the general color is deepened by the uniform but inconspicuous fine 

 pigmentation, which covers the back to about halfway to the lateral fine. On the 

 sides the pigment grows less and disappears entirely below the lateral line about 

 halfway to the belly. The pigment dots on the cranium, in the preorbital area, and 

 on the maxillary are abundant but so fine as to cloud only slightly the whiteness of 

 the cartilage; but in the prenarial region, on the premaxillaries, and on the mandible 



« 2 These and other figures, unless otherwise designated, are based on an examination of 163 specimens ranging in length from 

 225 to 402 millimeters. Values for both forms are grouped together as many specimens occur that are intermediate. The higher 

 values for L/D, Pv/P, Av/V, L/H, and for scales and scale rows are from typical artedi. 



*> Three hundred and thirteen specimens. 



** Seven hundred and fifty specimens. 



4S Forty specimens. 



