1164 
SCANDINAVIAN FISHES. 
tail is of a rounded quadrangular section, and is more 
or less deeply impressed in the median line above and 
below. Where the body is shallowest, just in front of 
the caudal fin, the breadth (thickness) is about 3 / 4 of the 
depth. The greatest depth measures about 137 2 (?) — 
1 1 1 / 2 (cf) %, and the least depth about 27 2 — 3 %, of 
the length of the body. The greatest breadth occurs 
in the head, just in front of the gill-openings, and is 
Fig. 341. Anterior part of the ventral side in a Sagre ( Etmopterus 
spinax ), ok 4 dm. long, from Stromstad Fjord. Nat. size. 
about 11 — 9 % of the length of the body. Across the 
gill-openings, on the other hand, the body is somewhat 
contracted, forming, as it were, a neck. 
The length of the head to the first branchial aper- 
ture measures in full-grown specimens about 1 7 J / 2 — 
17 %o a of the length of the body. Above the head is 
almost flat, underneath convex. Between the eyes the 
forehead is coursed by a longitudinal groove on each 
side of a terete median carina, which forks behind into 
two divergent branches. The interorbital width (in- 
cluding the dermal rim of the supraorbital margins) is 
about 45 %, and the length of the elongated, anteriorly 
and posteriorly pointed orbits about 31 %, of the length 
of the head. The eyes themselves are also elongated, 
the height of the iris being about 2 /s of its length, 
which is nearly 7s of that of the head. The length 
of the snout is about equal to that of the orbits, and 
in form the snout differs considerably from that of the 
preceding species, advancing with uniform breadth, 
until it is abruptly rounded off at the nostrils to a 
very blunt tip. The nostrils (fig. 341) are apparently 
double on each side, the small, pointed nasal valvules, 
one from the anterior margin, one from the posterior, 
laying their tips together, so that each nostril seems to 
consist of a circular aperture, situated at the very margin 
of the snout, and a proximal, oblong opening, directed 
obliquely backwards and inwards. Their entire breadth 
(both apertures) is about equal to the distance between 
their inner extremities, but only 7 3 °f that between 
the latter and the middle of the margin of the upper 
jaw, which margin lies below the posterior margin of 
the eyes, about half-way along the head. At the middle 
of the under surface of the snout is a longitudinal con- 
cavity which calls to mind the groove present at the 
same point in foetuses of the preceding species. Among 
the pores belonging to the system of the lateral line 
on the snout, a double row on each side of the median 
groove underneath and a similar series on the upper 
surface, in a loop above the nostrils, are especially pro- 
minent. At an angle to the last-mentioned series a 
row crooks over each eye and is continued back towards 
the occiput. The broad mouth is slightly curved, its 
breadth being about 3 / 7 of the length of the head, or 
somewhat greater than the distance between the nostrils 
and the upper jaw. The thin corners of the mouth 
are each surrounded by a deep groove, which is conti- 
nued backwards by a slit narrowing to a point. The 
upper jaw is armed with 3 or 4 transverse rows of 
tricuspid or quinquecuspid teeth, with the median cusp 
largest, one row close behind the other. The lower 
jaw contains only one row of simultaneously function- 
ing teeth, essentially similar to those of the preceding 
species, and forming, as there, a serrated cutting-edge; 
According to Lilljeborg 16 according to Krgyer sometimes 15Y 2 %. 
