MACKEREL. 
Ill 
Mode, Christ., 1868, p. 520; Malm, Gbgs, Boh. Fn ., p. 
408; Lillj., So., Norg. Fislcar , vol. I, p. 224; Jord., Gilb., 
Syn. Fish. N. Amer., Bull. U. S. Nat. Mus., No. 16, p. 424; 
Br. Goode. Fish. Industr. U. S., part. I, p. 281, tab. 91. 
Scomber scomber , Lin., Syst. Nat., ed. XII, tom. I, p. 492; 
Gthr, Cat. Brit. Mus., Fish., vol. II, p. 357; Coll., Vid. 
Selsk. Forb. Clirist. 1874, Tillsegsh., p. 43; 1879, No. I, 
p. 18; Winther, Naturh. Tidskr. Kblivn, ser. 3, vol. XII, 
p. 12; Id., Zool. Dan., Fiske, p. 21, tab. IV, fig. 3; Day, 
Fish. G:t Brit., Irel., vol. I, p. 83, tab. XXXII et XXXIII 
( var . punctatus); M6b., Hcke, Fische d. Ostsee, p. 38. 
The form of the body is handsome, elongated, 
terete and shallow; it tapers almost equally at both 
ends. The greatest depth, which is generally situated 
at the end of the first dorsal fin, varies according to 
age and sex between 15 % and 20% of the length. The 
greatest breadth, which is situated at the same point, 
is somewhat more than 2 / 3 of the greatest depth. Both 
the back and the belty are broad and convex, but the 
dorsal line is almost straight from the occiput to the 
second dorsal fin, from which point it slopes down to- 
wards the caudal fin. The ventral line, on the other 
hand, runs fairly evenly in a slight curve from the 
point of the lower jaw to the base of the caudal fin. 
The head is cuneiform, triangularly pointed and middle- 
sized. During the first year and up to the spring of 
the second its length is somewhat over 1 / i (between 
27 % and 25 %) of the length of the body; it then sinks to 
about 23 %\ but after the third year it apparently rises 
again to about 24 %. The perpendicular drawn from 
the occiput to the isthmus through the hind margin of 
the orbit is about half the length of the head, and the 
breadth of the latter, measured above the hind margin 
of the orbit, is equal to the distance between the tip 
of the snout and the anterior margin of the pupil. 
The breadth of the interorbital space at the middle of 
the eyes is on an average about 42 % of the length of 
the lower jaw up to the end of the first year, during 
the second year about 46 % and afterwards about 57 %. 
The snout elongated and pointed; the mouth of average 
size. The jaws are of equal length; when the mouth 
is open, the lower seems longer than the upper; but 
when the mouth is closed, it glides under the broad, 
flat preorbital bones. At the margin of the inter- 
maxillaries is a simple row of fine, pointed teeth of 
equal size, which are sparsely set and somewhat re- 
curved. A similar row of teeth also occurs at the 
margin of the lower jaw. The pharyngeals, too, are 
covered with long, setiform teeth, and there are about 
44 long gill-rakers on the front of the first branchial 
arch. At the margin of each palatine bone is a row 
of very small teeth, and laterally at each end of the 
head of the vomer we find from 2 to 4 somewhat 
larger teeth. The tongue is small and smooth, with 
the point free. The eyes of average size and set high; 
the diameter of the orbit measures about 1 / 5 of the 
length of the head. They are covered with a thin, 
transparent membrane, which, however, seems to grow 
thicker toward winter. This membrane — the so- 
called adipose lid, though there is no fat whatever in 
it (see above) — extends along the side of the head 
and envelops the eyeball, but always leaves uncovered 
a, perpendicular slit above the pupil. The anterior flap 
is continued some way over the posterior at the lower 
margin of the eye. The anterior nostril is, as usual, 
a round hole, and lies half-way between the tip of the 
snout and the anterior margin of the pupil: the poste- 
rior, as is also generally the case in the Scombridce, 
is a perpendicular slit, situated half-way between the 
anterior nostril and the anterior margin of the pupil. 
The apparatus of the gill-cover is made up of thin bones 
with smooth margins: the hind margin of the oper- 
culum is somewhat incised, its length (in the direction 
of the body) is about x / 5 (from 20 to 22 %) of the 
length of the head: along the preoperculum it is elong- 
ated downwards, over the suboperculum, into a point. 
The breadth of the back part of the interoperculum 
varies between 13 % and 16 % of the length of the head. 
The rounded lower corner of the preoperculum is elong- 
ated posteriorly in a downward direction. The striation 
of the margin of the preoperculum which we have ob- 
served above in Sarda pelamis, is not quite absent in 
this species, but is far more indistinct. The gill- 
openings are large. The branchiostegal membrane, 
which is free (not fastened at the isthmus) is supported 
by 7 rays on each side, the last two of which lie close 
together under the gill-cover. 
The body is covered with very small scales, which 
on the silvery belly can scarcely be distinguished with the 
naked eye; in the region of the pectoral fins and along 
the clavicular bones, the posterior boundary of the gill- 
openings, they are somewhat larger, but form no distinct 
corslet. The lateral line, which lies much nearer the back 
than the belly, begins at the upper margin of the gill- 
opening and extends in a sinuous line to the middle of 
the caudal fin. The vent is situated at the beginning 
of the last third of the length of the body, measured 
from the tip of the snout to the base of the caudal fin. 
