112 
SCANDINAVIAN FISHES. 
The first dorsal fin, all the rays of which are un- 
branched, is short, high and almost triangular, with 
the upper posterior margin concave. When depressed, 
it lies hidden in a deep groove in the back; the second 
ray is the longest and the last rays are very short. 
In a large specimen from the north of the Sound there 
are only 10 rays in this fin, and the last ray is so 
short that it- scarcely reaches half-way up the fin- 
groove. The second dorsal fin, which begins above 
the vent, is lower than the first, concave at the upper 
margin, half as high as it is long and covered with 
scales at the base. The anal fin begins a little farther 
back than the second dorsal, but it has the same form 
and the same covering of scales. The finlets behind 
the dorsal and anal fins consist of one ray, which is 
branched repeatedly, and are generally bent sideways 
in opposite directions on the back and the lower caudal 
edge. Thus, if the former are bent to the right, the 
latter are generally bent to the left. The pectoral fins 
are obliquely pointed and set, as is usual in the family, 
in a depression, so that there is no unevenness at the 
base when the fins are folded and laid back. In the axil 
a dermal flap, which is folded or at least dentat-ed at the 
margin, hangs down from the outside of the postclavi- 
cular bone. The ventral fins are inserted a little farther 
forward than the beginning of the first dorsal, and al- 
most vertically below the beginning of the third fifth of 
the length of the pectoral fins. They are narrow and 
obliquely pointed, are set close together and, like the 
pectoral fins, when folded, lie in a depression which 
has a dermal fold at the sides. The caudal fin is 
deeply forked, with narrow lobes, which are widely 
spread and have rounded points: the number of the 
rays, which it is difficult to distinguish on account of 
the thickness of the fin-membrane, is about 8 — {— 1 6 — 8. 
Though there is not the least external trace of a middle 
carina on the sides of the tail, we find a raised, bony 
ridge on the penultimate and the last caudal vertebrae. 
The colouring is so brilliant and variable that it 
is difficult to describe. The back and the forehead are 
dark green, with crooked, black transverse bands, some- 
times like fine streaks (var. scriptus ) and sometimes 
broken up into spots (var. punctatus), which extend 
down the sides somewhat below the lateral line"; be- 
tween these lines the colour is a bright bluish, shading 
a The colour of the back may sometimes be an unvaried black 
b Ofvers. Vet.-Akad. fork. 1876, No. 5, p. 71, tab. V. 
c Day, 1. c., p. 91. 
into greenish yellow. At the end of the dark trans- 
verse bands a more or less distinct, straight, black 
streak, which is sometimes broken up into spots, runs 
along the sides. From this point downward the co- 
louring becomes gold, silver and mother-of-pearl, shad- 
ing into red and yellow, while the belly is white. The 
sides of the head silvery: the margin of the mouth, 
the snout, the tip of the lower jaw, the inside of the 
branchiostegal membrane and sometimes the articula- 
tions of the gill-cover black: the first dorsal fin a clear, 
transparent gray. The second dorsal and the dorsal 
finlets blackish gray. The pectoral fins black at the 
base, especially on the inside, and gray at the point. 
The ventral and anal fins and the inferior caudal edge 
with its finlets white. The caudal fin dark gray. 
On examination of the internal organs we find 
that the long digestive canal consists of a wide oeso- 
phagus, running in a straight line with the stomach, 
which is pointed and extends to the region of the vent. 
Around the pylorus and duodenum are a large number 
of long, narrow pyloric appendages, which follow the 
intestine to its first bend, from which point its dia- 
meter varies very slightly, though it forms two more 
bencls. On the interior of the stomach are a large 
number of longitudinal folds, joined by fine, transverse 
wrinkles. The liver, which is situated far forward and 
for the most part to the left side, consists of one, large, 
thick lobe, which has an elongated point at its extre- 
mity. It is pale red in colour. The gall-bladder, which 
is long and narrow, lies on the right of the digestive 
canal. The spleen is small, oblong and blackish broAvn. 
The kidneys, Avhich are narroAver behind than in front, 
are almost as long as the abdominal cavity. No air- 
bladder. r IVo ovaries, as long as the whole abdominal 
cavity. The eggs fairly small. The milt-sacs of the 
same form as the ovaries. Malm has described herma- 
phrodites of this species 6 . All the statements as to an 
external difference of sex in the Mackerel Avhich have 
been made up to the present, have proved untrust- 
worthy on closer examination. 
The usual length of the Mackerel is betAveen 3 and 
4 dcm. 'Off the English coasff, however, specimens 
have been found, though seldom, 470 mm. in length; 
and Artedi, as Avell as Strom, mentions specimens, 
the length of Avhich Avas 594 mm. The species occurs 
(Collett: N. Mag. Naturv. 1884, p. 58). 
