458 
SCANDINAVIAN FISHES. 
Naturv. Christ., Bd. 29 (1884), p. 101; Lillj., Sv., Norg. 
Fn ., Fisk., vol. 2, p. 350. 
Pleuronectes Inrtus, Abildg. apud Mull., Zool. Dan., vol. Ill, 
p. 36, tab CIII; Betz., Fn. Suec. Lin., p. 333; Nilss., 
Prodr. Ichth. Scand., p. 59; Gottbche (Zeugopterus), Wiegm. 
Arch. Naturg., I, 2, (1835), p. 178; Fries ( Pleuronectes ), 
Vet.-Akad. Handl. 1838, p. 184; Yaiir (Rhombus), Brit. Fish., 
ed. 1, vol. I T, p. 243; Parn., Mem. Wern. Soc., vol. VII, 
p. 376; Kr., Damn. Fiske, vol. 2, p. 445; Nii.ss., Slcand. 
Fn., Fisk., p. 646; Mor., Hist. A'at. Poiss. Fr., torn. Ill, 
p. 321. 
Mullers Topknot, Couch, Fish. Brit. Isl., vol. Ill, p. 170, 
tab. CLXV. 
Muller’s Topknot attains a length of about 25 cm. 
The body is elliptical and of more uniform depth than 
in the preceding genus, the greatest depth of the body 
remaining almost unchanged for some distance, about 
half-way between the tip of the snout and the caudal 
fin. The depth at this spot varies, at least after the 
fish has attained a length of 90 mm., between 46 and 
51 % of the total length of the body, the proportion 
rising fairly regularly with age. In front the body is 
almost semicircular, behind more elongated, the least- 
depth (across the peduncle of the tail) varying between 
6 1 ,/ 2 and 8 % of the total length of the body, and 
also increasing, even relatively, with age. The form 
of the body is most affected, however, by the dorsal 
and anal tins, which increase in height posteriori)’, while 
the depth of the body itself diminishes. When these 
fins are taken into account, the body is deepest at about 
the beginning of the fourth quarter of the distance be- 
tween the tip of the snout and the base of the caudal 
fin. This depth is about 66 or 68 % of the total length 
of the body. The greatest thickness of the body in 
old specimens is distinctly greater than in the pre- 
ceding genus, increasing with age from about 8 to 9 % 
CO' O C 
of the length of the body. 
The most remarkable point in the form of the head 
is the sharp ascension of the cleft of the mouth. When 
the month is closed, the jaw-bones, at least the maxil- 
laries, assume an almost perpendicular position; but the 
mouth is also highly protrusile, much more so than in 
the preceding genus. The intermaxillary bones may 
be shot forward for a distance equal to the length of 
the snout proper; the lower jaw is then horizontal, the 
branches of the intermaxillary bones place themselves 
at right angles to it, and the lower end of the maxillary 
bones is directed obliquely forward. The jaw-bones are 
fairly symmetrical, those of the eye side being only 
slightly longer than those of the blind side, or equal 
to them in length. Just as the head as a whole is 
comparatively larger than in the preceding species — its 
length undergoes even relative increase, during the 
growth of the fish, from 2 6 7, % to rather more than 
28 % of the length of the body — the jaws are also 
even relatively longer than in Ekstrom’s Topknot. The 
length of the branch of the lower jaw on the blind side 
increases with age from about 12 to nearly 14 %, that 
on the eye side from 13 to a little more than 14 %, of 
the length of the body; and the corresponding alterations 
in the maxillary bones are from about 1 0 1 / 2 to 12V 2 % 
(sometimes nearly 13 %) of the length of the body. 
The length of the lower jaw, however, is always less 
than that of the head behind the lower eye, which in- 
creases with age from about 1 4 l / 2 to 1 6 \ 2 % of the 
length of the body. The eyes are fairly large, their 
longitudinal diameter relatively decreasing during growth, 
from about 38 V 2 to 25 '/ 2 % of the postorbital length 
of the head; but they are comparatively smaller than 
in either of the two preceding genera. Their position 
in relation to each other continues to change at a late 
period in the growth of the fish: when the fish is 17 
cm. long, we may find the eyes still almost abreast of 
each other, while in specimens 2 dm. long the wander- 
ing (originally the right) eye may have retired half its 
diameter behind the lower eye. There is no intruding 
lobe from the iris into the pupil; but the rough skin 
that covers the inner (in the lower eye the upper, in 
the upper eye the lower) part of the eye, projects in 
a more or less arcuate form out over the pupil. The 
interorbital space is not remarkably broad in comparison 
with its breadth in other Bothince, but it is broader 
than in the two preceding genera, its least breadth va- 
rying in this species between 30 and 45 % of the lon- 
gitudinal diameter of the eye. It is only on the eye 
side that the nostrils are always distinct, or at least the 
anterior, with its foliate dermal flap. On this side they 
are set close to each other, on about a level with the 
middle of the interorbital ridge, and the posterior just 
in front of the perpendicular from the anterior margin 
of the lower eye. On the blind side they are extremely 
small — where they are present at all — as fine as the 
pores of the lateral line, and in most of our specimens 
they are impossible to detect in the loose skin that 
covers, the nasal cavity, just behind the articulation of 
the maxillary bone, below the second and third rays 
of the dorsal fin. In one of our specimens they are 
present in the form of open, but extremely small holes, 
in another they are somewhat larger, but covered by 
