184 
SCANDINAVIAN FISHES. 
membrane, which is supported by six rays, is united 
under the middle of the throat (the isthmus) to the 
corresponding membrane on the other side by a con- 
tinuation of its skin, which is here of almost the same 
breadth as itself, and lias an even, transverse margin, 
posteriorly free. When both the branchiostegal mem- 
branes are expanded, there thus appears a large arcu- 
ate collar round the head. The nostrils are small, 
forming on each side two funnel-shaped, dermal ducts, 
which are separated by the nasal bone, the one open- 
ing lying on the side of and close to the anterior mar- 
gin of the eve, the other in front of the latter and 
somewhat nearer it than the tip of the snout. The 
eyes (cf. the above table) are fairly large — their longi- 
tudinal diameter varies between 2 / 9 (in young speci- 
mens) and V 7 (in old) of the length of the head — 
and so close together that the space between them, 
which is concave, is narrower than their diameter. The 
pupil is round; in some specimens oval, with the more 
pointed end directed forwards.. The head is armed with 
several spinous processes — first with two, pointed, 
conical spines in front of the eyes and between the 
nostrils, projecting from the sides of the nasal bone 
and movable; and secondly with four fixed spines on 
its top, which point in a backward direction, one at 
the superior margin of each eye and one on each side, 
at the end of the occiput. Between the latter runs a 
bar on each side of the top of the head, that on one 
side being nearly parallel to that on the other. The 
four last spines, which look like small horns, have given 
rise to the name of Hornskalle (Hornhead). Sometimes 
they are wanting, and in their stead we find more or 
less sharp tubercles. The fishermen hence believe that 
these horns are shed or knocked off in some way du- 
ring the spawning-season. On the margin of the pre- 
operculum we generally find three (sometimes four) 
strong spines. The uppermost is the largest and points 
in a backward direction; it never extends so far back, 
however, as the opercular spine, which points in the 
same direction as it. The second is next to it in size 
and also directed backwards: sometimes the tips of both 
project above the thick skin which covers them. The 
other two are short and flat; the fourth points down- 
wards and the third is often wanting, or present on 
one side of the body and wanting on the other. The 
operculum ends in a long, projecting spine (the oper- 
cular spine) and a still longer, thin, dermal margin. 
The suboperculum has two spines in its lower margin; 
the one points downward and is the longer, the other 
is turned inwards in a forward direction and is hidden 
by the preoperculum. The interoperculum, as usual, 
has its upper posterior corner prolonged into a spine, 
which is directed backwards, but is scarcely visible, as 
it lies under the point of the downward spine of the 
suboperculum. There is also a long spine, which lies 
under the skin and is directed backwards, on the true 
clavicular bone, and a similar one on the upper cla- 
vicular bone. The lateral line is raised, but totally 
unarmed. It lies near the back, and follows the dorsal 
curve to the end of the second dorsal fin, at about the 
30th pore in the line counted from the beginning, 
where it curves slightly downwards and then termin- 
ates at the middle of the base of the caudal fin. On 
each side of the line are scattered irregularly strewn, 
stiff scutes, of a singular nature, generally differing in 
the different sexes. In the male they are large, flat, 
rounder, depressed at the centre and cup-shaped, with 
from 3 to 5 or more stiff points, turned outwards in a 
backward direction or set in the margin of the whole 
scute; in the female they are smaller and narrower, 
nearly oblong, with only 1 or 2 spines. In the latter 
sex, too, they are not always present, for one may find 
specimens entirely without them, others with extremely 
few, and so forth. The body tapers conically towards 
the tail and is rounded, with the caudal part laterally 
compressed to some extent. The back, which rises 
somewhat, to the 3rd fin-ray and then slopes evenly 
towards the tail, has its two fins quite distinct, but often 
set very close together. The first dorsal fin is more 
convex, shorter and lower than the second; its two first 
rays are usually close together at the base. In Scandi- 
navian specimens the number of rays varies between 
8 and 10, all simple, pungent and curved slightly back- 
wards; in Arctic specimens it is most often 11. The 
posterior dorsal fin is larger, with rounded margin, and 
in Scandinavian specimens contains from 14 to 16, in 
Arctic often 17 and sometimes even 19, simple, articul- 
ated and weak rays. The pectoral fins are large, as is 
the rule in the genus, oblong and rounded, with from 
15 to 17 simple, articulated, round and thick rays. The 
7th and 8th rays are the longest, and the fin then 
sharply diminishes in length to the last ray, the length 
of which is only V 2 or 1 / 3 of that of the first (upper- 
most) ray. As is generally the case in the genus, the 
tips of the lowest rays extend somewhat beyond the 
fin-membrane. The ventral fins are long (cf. the above 
