BURBOT. 
533 
the Burbot of the Old World. Though the length of the pectoral fins is 
extremely variable — the variations extending in our Burbot between 
13 and 21 % of 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 fins and a relative de- 
crease in their length seem to be changes of growth that might well 
explain the difference maintained by Lutken, or at least impair its 
validity. This is the reason why we have 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 the purely 
Arctic Burbot of the Old World are allied in form to the American 
Burbot, for, according to Collett, there is a wide gap in the range 
of the Burbot in Norway. Our collections are not extensive enough 
to enable us to decide this question. 
In central Sweden the ordinary length of the Bur- 
bot is about two feet (600 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 3 / 4 lbs. (6,375 grammes). A Burbot 13 lbs. 
(6,460 grammes) in weight was caught in a trap (ryssja) 
in Kyrkviken off Lidingo, on the 7th of January, 1887. 
It is, however, 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 60 lbs. (27V 5 
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- fishes ’ ; 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 firmly attached, and may be 
easily extracted with a penknife or the point of a 
needle. In a fish 6 dm. long the largest scales are 
hardly l 1 / 2 mm. in breadth. They cover the skin en- 
tirely, out over the snout and the fins, where they are, 
however, very small. 
The head is small. In a middle-sized Burbot its 
length, including the whole gill-cover, is only about 
v 5 (21 to 19 V 2 %) of the length of the body. Its length 
seems to be more subject to individual variations than 
to changes of growth. Seen from above its appearance 
is parabolical, rounded in front. The upper surface is 
strongly depressed, flat, and smooth. The head may be 
expanded to a breadth much greater than that of the 
body, but when the jaws and the gill-covers are closed, 
it is much narrower than the forepart of the trunk. 
The eye is round and deeply imbedded in a rather 
oblong socket without distinct margin. In specimens 
between 22 and 90 cm. long the longitudinal diameter 
of the eye varies between about 187 2 and 1 1 1 / 3 % of 
the length of the head, between about 62 and 37 % 
(sometimes 35 (A %) of the length of the snout, or be- 
tween 85 and 36 % 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 
brown with silvery inner margin and round pupil. The 
tip of the snout projects a little beyond the anterior 
margin of the upper jaw. The two nostrils on each 
side are rather small, at least the anterior ones, which 
lie about half-way between the eye and the tip of the 
snout, and have the prominent hind margin elongated 
into a soft, flat filament, about half as long as the eye 
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 upper (inner) part thereof gener- 
al]}' 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 mouth 
extends below the anterior margin of the eye. The 
margin of the upper jaw is formed by 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 maxil- 
lary 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 Bean’s (1. c.) comparison between European and American Burbot it appeared that the number of the vertebra? was the only 
constant distinction between these forms; but Kroyee states that the number of vertebra? in the European form is 21+37, and Malbi found 
22 + 40. In a skeleton in the Royal Museum we find 23 + 39. 
