SCANDINAVIAN FISHES. 
670 
extreme front of its dorsal plane with two unpaired 
plates, which have been called occipital, because their 
middle carina forms a continuation of the occipital 
carina. These plates also lie so far forward that the 
anterior one partly covers the crest of the occiput, and 
the small gill-openings lie beside the front part of the 
posterior plate. Thus the hind part of the head with 
the gill-openings lies to a great extent within the limits 
of the trunk. The anterior occipital plate is shorter 
than the posterior, sometimes only half as long. The 
true occipital carina is hardly as high as these so-called 
occipital plates; but still the occiput rises considerably 
from the forehead, which in its turn slopes forward 
towards the snout. The occiput is also convex, and the 
sides of the hind part of the head are considerably 
tumid, on account of the alveated form of the oval 
opercula. These bones are striated with smooth ridges, 
radiating upwards and downwards and leaving between 
them rows of small cavities in the surface; and an hori- 
zontal ridge, granulated by a row of small round tu- 
bercles and scarcely half as long as the operculum, runs 
back from the articulation of this bone. The occiput, 
the top of the head, and the temples are cavernous 
in the same manner, but with coarser and more irre- 
gular depressions. The snout, on the other hand, is 
smooth, with the exception of the bars (carina?) that 
follow its dorsal side. One of these bars, the dorsal 
carina of the snout, runs in a line with the occipital 
carina, which has terminated and been obliterated on 
the concave forehead. This bar is coasted on each side 
by another, an immediate continuation in a forward 
direction of the strongly elevated upper orbital margin, 
which is continued backwards in the same manner by 
a ridge that runs obliquely up towards the beginning 
of the anterior occipital plate. The orbital margin itself 
is also continued downwards and sharply defined in old 
specimens, in which the praefrontal bone also forms a 
prominent knob at the middle of the anterior orbital 
margin. All these ridges are granulated at the free 
margin, more or less distinctly and most so in old spe- 
cimens, by a row of small round tubercles. In front 
of the said praefrontal protuberance, which is not very 
distinct in young specimens, lies a triangular depression, 
within which an obliquely longitudinal elevation of the 
skin bears a small round nostril at each end. When 
the mouth is closed, the snout is somewhat compressed 
from the sides, with the breadth gradually decreasing 
in front; but when the mouth is open, it is more terete 
and, when seen from above, of more uniform breadth. 
The tip of the snout is turned upwards, and rises per- 
ceptibly above the ascending tip of the lower jaw. 
The length of the snout varies considerably in 
different individuals, but especially according to age. 
In young specimens, up to a length of 2 dm., it may 
be only slightly greater or even somewhat less than half 
the length of the head; but in older specimens it mea- 
sures about 56 — 59 % thereof. The variation is as 
great, but reversed, in the case of its least depth, which 
we have found in young specimens to measure 20 — 18 
% of its length, while the corresponding proportion in 
old specimens varies between about 15 and 13 %. As 
a rule the least depth of the snout is 2 /s of the length 
of the lower jaw, which is about the same as the dia- 
meter of the eyes. The postorbital length of the head, 
occupied almost entirely by the gill-cover, measures about 
V 8 (31 — 34 %, exceptionally 36 %) of its entire length. 
As we have mentioned above, the branchiostegal 
membranes are entirely coalescent, below and on the 
sides, with the front of the shoulder-girdle. The gill- 
openings, with their crescent- shaped lids, are small hori- 
zontal crevices, about half as long as the diameter of 
the eyes, and situated in a line with the latero-dorsal 
carina? of the trunk, which begin just behind them. 
The only paired fins, the pectorals, occupy an obli- 
quely vertical position about half-way up the body, and 
are of almost uniform breadth, with sharply rounded 
tip. Their rays are simple and unarticulated, somewhat 
widened at the tip, and usually 12, exceptionally 10 — 
13, in number. The length of the longest (middle) 
rays is always less than the depth of the body at the 
beginning' of the tail. 
The dorsal fin begins on the last or the penulti- 
mate ring of the trunk, at a distance from the tip of 
the snout which we have never found to exceed 39 % 
(37 — 38 1 / 2 %) of the length of the body, and which is 
greatest as a, rule in the females. It is of almost uni- 
form height, though it rises slightly in a backward direc- 
tion for about three-fourths of its length and then sinks 
again. Its rays (usually 35 — 42, exceptionally 43 — 45), 
like those of the other fins, are simple and unarticulated; 
they are somewhat broader at the tip and compressed 
(flattened in the longitudinal direction of the body). 
It more or less entirely occupies 10 or 9 rings of 
plates, and the length of its base, which is always 
shorter than the head, measures 11 or 12 % of that 
of the body. 
