GREAT LAKES COREGONIDS 



363 



LEUCICHTHYS ALPENA Koelz 



The Longjaw (Fig. 15) 

 Leucichthys alpenas, Koelz, 1924, pp. 1-5; Lakes Michigan and Huron. 



Argyrosomus prognathus Evermann and Smith, 1896, pp. 314-317; in part, Lakes Michigan and 

 Huron. 



Leucichthys johannx Jordan and Evermann, 1911, pp. 24-25, in part, Lakes Michigan and Huron 



The longjaw is described from Lake Michigan and is known to occur only in 

 Huron of the other lakes of the Great Basin. In both lakes the species is charac- 

 terized by the large size it may attain, its pale color, its long mandible, relatively 

 short paired fins, and the moderate number of gill rakers on the first branchial arch. 

 It seems to prefer moderate depths in both lakes and spawns in late November. 

 The Huron form has been found to differ from the typical form only in having on 

 the average somewhat fewer gill rakers and lateral-line scales and a somewhat 

 longer head. 



Type 



The type is a female specimen (catalogue No. 87352, U. S. National Museum) 

 269 millimeters long, collected on June 15, 1923, 22 miles NNE. of Charlevoix, Mich., 

 off He aux Galets in 25 to 47 fathoms. 



Leucichthys alpencs of Lake Michigan 



The longjaw is the largest Leucichthys in Lake Michigan. Specimens not 

 infrequently attain a length of 38 centimeters (15 inches) and a weight of 2 pounds. 

 The body is compressed, fusiform, and rather elongate. The greatest depth, through 

 a point just in front of the dorsal, comprises in adult specimens 23 to 26 per cent of the 

 total length. Gravid females are often deeper, of course. The width is about 50 to 

 55 per cent of the depth. The anterior dorsal profile of the body usually rises grad- 

 ually from the occiput to the insertion of the dorsal, but it is sometimes somewhat 

 steeper over its anterior half, particularly in the largest specimens. Behind the 

 dorsal the line continues in a very faint curve to the caudal peduncle. The ventral 

 profile is rather strongly and uniformly curved from the tip of the snout to the caudal 

 peduncle. There is a tendency for the contour line between the ventrals and the anal 

 to become straight and parallel to the lateral line, however. The head, which is 

 relatively short and deep, is contained 4.4 [(3.8) 4.1-4.4 (4.6)] 18 times in the total 

 length of the fish. In side view it is broadly triangular. The dorsal profile usually is 

 faintly convex and forms a smooth arc continuous with that of the first half of the 

 predorsal body contour. The degree of its convexity is greatest in those specimens in 

 which the premaxillaries approach a vertical position. The premaxillaries may be 

 immaculate but usually are more or less pigmented and are directed forward, ordi- 

 narily making an angle of 45° to 60° with the horizontal axis of the head. The snout, 

 seen from the side, is broad and rounded. It is contained 3.7 [(3.3) 3.4-3.6 (4)] 19 

 times in the head. The maxillary is nonpigmented in about 90 per cent of over 500 

 specimens examined and extends beyond the anterior edge of the pupil but seldom 



u The figures given in brackets, unless stated otherwise, are based on an examination of 289 specimens (paratypes) ranging in 

 length from 205 to 386 millimeters. 

 11 Seventy-five specimens. 



