BURBOT. 



533 



tin' Burbot of Uic- Old World. Tliougli the longlli of the pectoral fins is 

 extremely variable — tlie variations extending in our Burbot between 

 13 and 21 % oi the length of the body — but in the Old World we 

 have never found it to be less than 13 %. On the other hand, the 

 removal in a backward direction of the- dorsal tins and a relative de- 

 crease in their length seem to be changes of growth that might well 

 explain the difference maintained by Lt'TKEN, or at least impair its 

 validity. Tliis is tlic reason wliy we has'e not considered it necessary 

 either to refer the specimen from the Yenisei to the American form, 

 or even to regard the two forms of the Burbot as entirely distinct 

 from each other", though there is a possible chance that tlie purely 

 Arctic Burbot of the Old World are allied in form to the American 

 Burbot, for, according to Coi.lett, there is a wide gap in the range 

 of the Burbot in Norway. Our collections are not extensive enough 

 to enable lis to decide this question. 



In central Sweden the ordinaiy length of the Bur- 

 l)ot is al)oiit two feet (60(J mm.). In the south of 

 Sweden it seldom attains this length. A Burbot 57 

 cm. long has been found to weigh 1,487 grammes, one 

 5 dm. long nearly 850 grammes, and a specimen 4 dm. 

 long 425 grammes. Thus in these cases the weight 

 increased in direct proportion to the cube of the length. 

 The largest Burbot Sundevall ever saw, was taken 

 about 1840 in Lake Bafven in Sodermanland, and 

 weighed 12% lbs. ((i,375 grammes). A Burbot 13 lbs. 

 (G,4G0 grammes) in weight was caught in a trap (ri/ssja) 

 in Kyrkviken off Lidingo, on the 7th of January, 1887. 

 It is, liowever, only exceptionally that Burbot more 

 than two kilogrammes in weight are found in Sweden. 

 The species attains a much larger size in the Arctic 

 regions. As we have mentioned above, the Royal Mu- 

 seum possesses a specimen 9 dm. long from the Ye- 

 nisei; and Dall states, according to Bean (1. c), that 

 in Alaska the Burbot attains a weight of (30 lbs. (27 '/j 

 kgm.), which according to the proportion assumed above 

 presupposes a length of 13 or 14 dm. Thus the Bur- 

 bot in size rivals the Ling. 



The skin is rather thick and uncommonly strong, 

 almost like that of the Eel; and there are many points 

 of resemblance between these two fishes. The scales 

 are very small, as in the other species known by the 

 fishermen as 'skin-fisJies' : but they are distinctly visible 

 through the slimy epidermis, in which they lie flat and 

 close together, each scale entirely enclosed in a follicle. 

 They do not seem to be firmlv attached, and may be 

 easily extracted witli a penknife or the point of a 

 needle. In a ii.sh G dm. long the largest .scales are 

 hardly V,\ mm. in breadth. They cover the skin en- 



tirely, out over the snout and the tins, where ihcy are, 

 however, very small. 



The head is suiall. In a middle-sized Burbot its 

 length, including the whole gill-cover, is only about 

 Vj (21 to 19', %) of the length of tlie body. Its length 

 seems to be more subject to iiidi\i(liial variations than 

 to changes of growth. Seen from above its appearance 

 is parabolical, rounded in front. The u])])er surface is 

 strongly depressed, flat, and smooth. Tlie head may be 

 expanded to a breadth much greater than that of the 

 body, but when the jaAvs and the gill-covers are clo.sed, 

 it is much narrower tlian the forepart of the trunk. 

 The eye is round and deeply imbedded in a rather 

 oblong socket without distinct margin. In specimens 

 betAveen 22 and 90 cm. long the longitudinal diameter 

 of the eye varies between about 18' ^ and II '/g % of 

 the length of the head, between about 62 and 37 % 

 (sometimes 35'., %) of the length of the snout, or be- 

 tween 85 and 3G ?o of the breadth of the interorbital 

 space. Its centre lies at about the end of the first 

 third of the length of the whole head. The iris is dark 

 bro^\■n with sihery inner margin and roinid pupil. The 

 tip of the snout projects a little beyond the anterior 

 margin of the upper jaw. Tlie two nostrils on each 

 side are rather small, at least the anterior ones, which 

 lie about half-wa^- between the eye and the tip of the 

 snout, and have the prominent hind margin elongated 

 into a soft, flat filament, about half as Ions as the eve 

 or a little longer. The posterior nostril is generally 

 distinctly larger, and lies half-way between the eye and 

 the anterior nostril or nearer the former. Its margin 

 is not raised, but the upiicr (inner) part thereof gener- 

 nll\- projects in a rounded shape over the opening, 

 which thus becomes kidney-shaped. The barbel under 

 the chin is longer than the eye. The cleft of the moutli 

 extends below the anterior margin of the eye. The 

 margin of the upper jaw is formed hj the intermaxil- 

 lary bones alone, which are not protrusile, but have 

 their front margin set below and, as we have men- 

 tioned, a little behind the tip of the snout. The niaxil- 

 lar^■ bones extend far behind the intermaxillaries, below 

 the middle of the eye, to a distance from the tip of 

 the snout of between 8 and nearly 10 ^ of the length 

 of the body or 41 and 45 % of that of the head. The 

 lower jaw is flat; its articulation lies somewhat behind 



" From Bkan's (1. c.) comparison between European and American Burbot it appeared that liie number of the vertebra; was the only 

 constant distinction between these forms; but Kroyer states that the number of vertebra^ in the European form i.-; 21+37, and M.\lm found 

 22 + 40. In a skeleton in the Koyal Museum we find 23 + 39. 



