956 
SCANDINAVIAN FISHES. 
the maxillaries we have to distinguish, as among the 
Vendaces, between the more terete, introrse, articular 
shaft, which supports the intermaxillaries on its up- 
turned, grooved, and proximally broader, front surface, 
and the lateral part, set almost at right angles to the 
former, and indeed terete in front, but soon expanding 
into the flat, sabre-shaped disk that forms the exter- 
nally visible maxillary. This part is obtusely rounded 
behind and toothed with spines at the thin lower mar- 
gin, and by the addition of the supplementary bone is 
rendered fairly uniform in breadth throughout the 
greater part of its length. The posterior supplementary 
(jugal) bone is elliptical, and in front pointed, the an- 
terior narrower and of uniform breadth. The length 
of the lateral maxillary disk, measured from the arti- 
cular knob, varies on an average between 10 and 87 2 % 
of that of the body or between 47 and 4472 % °f that 
of the head, and the bone extends back to a line with 
the anterior margin of the pupil or even with its centre, 
though always so that the length of the cheek (between 
the maxillary and the vertical anterior margin of the 
preoperculum) is greater than its height exactly below 
the eye. The cheek is covered by the large, third 
suborbital bone, which also forms the greater part of 
the posterior limit of the orbit, the fourth (hindmost) 
suborbital bone being comparatively short. The lower 
jaw is characterized by the rather great height of the 
dental part — about twice the breadth of the maxillaries 
or 7 5 °f the length of the lower jaw — and by the ter- 
ete ridges on the outside of this part, which diverge 
backwards from each side of the chin, one of them run- 
ning along the upper margin, the other parallel to the 
lower margin. The symphysis is also fairly high, and 
is furnished below with a small, prominent chin-protu- 
berance, but channelled underneath at its angle. Only 
at the extreme front of the upper margin do we find 
an arcuate row of small teeth (6 on each side of the 
symphysis), in well-marked, but closely approximated 
sockets. The length of the lower jaw varies between 13 
and 12 % (in the oldest specimens 11 %) of that of the 
body, or 60 and 57 % (exceptionally 61 % or, in the 
oldest specimens 55 %) of that of the head, and it is 
greater, as a rule, than the length of the base of the 
anal fin, though in exceptional cases this relation too 
is reversed. On the symphysis and the sides of the 
lower jaw hangs a fairly broad labial fold. Internally 
the mouth is furnished with the ordinary transverse 
folds (vela), the lower being the more developed. The 
vomer has in front a longitudinal, lanceolate elevation, 
bearing a double row of small, pointed teeth, somewhat 
larger, however, than the jaw-teeth ; and a shorter row 
of smaller teeth usually occupies the extreme front of 
each palatine. The tongue is free and fleshy, but thin- 
margined. On the glosso-hyoid bone is an almond- 
shaped card of small teeth. The gill-rakers are set in 
a single row on most of the branchial arches, long and 
setiform, with numerous small spines on their sides. 
On the first branchial arch there are about 70, as a 
rule 45 — 47 (exceptionally 44 or 50) on the lower part 
thereof, and the longest (at the middle of the arch) are 
about equal in length to the suboperculum at its suture 
with the operculum. Only on the upper part of the 
third arch and on the fourth arch as far as it forms 
the anterior margin of the short, hindmost gill-slit, do 
we find an inner (posterior) row of short, lamellate 
rakers. About 20 spines, similar in form to the latter, 
occupy the outside of the lower pharyngeals, which re- 
semble branchial arches, and are furnished with only 
one row of small teeth, whereas the upper pharyngeals 
bear a triangular card of similar teeth. The outer gill- 
openings are large, extending above the upper margin 
of the operculum, from a level with the superior mar- 
gin of the eye, down to a line with the anterior margin 
of the latter. The operculum is obliquely quadrilateral, 
with the upper posterior corner rounded and the lower 
anterior corner prolongated to an acute angle, so that 
the faint S-shape of the subopercular suture is directed 
obliquely backwards and upwards. The length of this 
suture varies between 23 (exceptionally 2 1 1 / 2 ) and 26 
(exceptionally 27) % of that of the head. On the sur- 
face of the operculum we can distinguish three slightly 
convex patches, separated by two shallow grooves, one 
running obliquely backwards and upwards, the other 
obliquely backwards and downwards, from the articular 
head of the operculum. But these patches are smooth 
or marked only with faint concentric s trial, and the an- 
terior lower patch in particular is destitute of radiating 
grooves or ridges. The suboperculum resembles a nar- 
row, eccentric sector of a circle, varying in breadth; 
sometimes its margin shows an irregular, shallow in- 
dentation. The preoperculum is obtuse at the inner 
angle, but the lower posterior corner forms a rounded 
right angle. Its posterior disk is so broad that its length 
(the lower arm together with the disk) is about equal 
to its height (the vertical arm together 'with the disk). 
The interoperculum is triangular and equal in length 
