878 
SCANDINAVIAN FISHES. 
quadrangular shape, with somewhat convex upper mar- 
gin, and with the hindmost ray measuring about 2 / 3 
of the longest ray. The shape and structure of the 
adipose tin have already been noticed. It is situated 
above the posterior three-fifths of the base of the anal 
fin, but the distance between it and the caudal fin 
(about 7 — 11 % of the length of the body) is in ge- 
neral perceptibly greater than that between the anal 
tin and the latter. The anal fin begins at a distance 
from the articular knobs of the maxillaries in the males 
equal to about 2 / 3 (66 — 68 V 2 %), in the females nearly 
3 / 4 (71 — 7272 % )-> °f the length of the body. The 
sexual difference in the base of this fin we have al- 
ready remarked. The length of its base is in the males 
about 17 — 19 % , in the females about 13 — 15 %, of 
the length of the body. Its lower margin is arcuate, 
and its height (the length of the longest, the 5th or 
6th ray) is always less than half" (38—47 %, excep- 
tionally 49 %) of its length (base). The caudal fin is 
as a rule somewhat less deeply forked than in the 
Smelt, the length of the middle rays being about 43 
— 53 % of that of the longest ones and usually greater 
than the least depth of the tail, only exceptionally, 
and then in the males, equal to the latter. The length 
of the middle rays varies between about 5 7 2 and 6 1 / 2 
% (exceptionally 7 %), and the length of the longest 
rays between about 12 and 14 %, of that of the body. 
The pectoral fins are set low, as in the Smelt, 
and the great sexual difference lies not only, as we 
have mentioned above, in the length of the fins, but 
also in their breadth. In the males, when the fins are 
folded, one of them overlaps the other under the belly 
to a considerable extent. When expanded, the two 
fins together form in the males almost a semicircle. 
In the females they are of a broad oval shape. Their 
length varies in the males between about 15 h and 
16 7 2 0// °i in the females between about 10 and 137' 2 
of that of the body. As a rule even their relative 
length increases with age, the females thus representing 
the lower grades of development. The ventral fins 
resemble the pectoral both in shape and sexual dif- 
ference, though the latter is less marked, and the 
ventral fins of the males together compose, more cor- 
rectly speaking, a half-ellipse. Their length is also on 
an average equal to that of the pectoral. They are 
inserted almost vertically belotv the beginning of the 
true dorsal fin, comparatively further back in young 
Capelins than in old and in the females than in the 
males, the average preabdominal length being in young 
females 31 7 2 in old females 327 2 %, in the males 
30 7 2 %>, of the length of the body, and the average 
postabdominal length in the females 1 8 1 / 2 %, in young 
males 1 8 1 / 3 %, in old males 1 7 1 / 2 %, of the length of 
the body. 
The scales are thin and small, as we have men- 
tioned above, but in essential respects (fig. 220, a) re- 
semble those of the Smelt, both as regards shape and 
c ha 
Fig. 220. Scales from the left side of a Mallotus villosus, 1 2 1 /, 
times the natural size, a, one of the ordinary scales below the lateral 
line in a female; b , a scale from the lateral line of a female; c, one 
of the larger scales at the base of the anal fin in a male; d. one 
of the villiform scales in the lateral band of a male, with the epi- 
dermal covering preserved, and with lobes of the torn dermal follicle 
(corium) on each side. 
texture, only that the concentric strife are few and 
scattered (usually no more than 5 or 6 behind the 
indistinct nucleus of the scale, 3 in front of the same), 
and interrupted at the top and bottom of the scale. 
The scales of the lateral line ( b ) have the same open 
incision in the hind part, and the duct is simply cana- 
liculate, nowhere closed by the elevated margins. The 
rule for the growth of the scales in the lateral line 
being that the duct is at first canaliculate, these scales 
accordingly occupy in the Capelin a lower develop- 
mental rank than in the Smelt. In the males, as we 
have mentioned above, scales of a special' shape appear 
“ In the Smelts always greater, 68 — 84 / in Osmerus eperlanus. 
h In exceptional cases we have found the pectoral fins of a male to measure only 14‘7 % of the length of the body. 
