MULLERS TOP Iv N 0 T . 
459 
skin. The operculum and suboperculum resemble those 
of the preceding species; but the interoperculum is still 
more tapering in front than in Ekstrom’s Topknot, with 
a distinct sinus in the lower margin, and also more 
distant from the lower jaw, to the angular part of which 
it is united by ligaments and rough skin. 'The pre- 
operculum is obtuse-angled, with a sinus in the hind 
margin just above the angle. The jaw-teeth in front 
form a dense and tine card. The palatal folds are well- 
developed, but in the upper jaw no broader than the 
card of teeth, in the lower jaw still narrower. The gill- 
rakers are set in a single row on the first branchial 
arch, as in most of the Botkina;, but are rather numer- 
ous, about 23 on this arch. The lower pharyngeals 
are distinctly narrower than in Ekstrom’s Topknot and 
without any marked expansion for the patch of teeth: 
they are furnished with only four or five rows of teeth, 
pointed like the jaw-teeth but straight. 
The margin of the body is entirely surrounded 
with fins, with the exception of the small sections oc- 
cupied by the lower jaw, the intermaxillary bones, and 
the extremely short peduncle of the tail. The dorsal 
fin begins so far forward that its commencement, which 
forms a lobe on the blind side, covers even the upper 
end of the maxillary bone; while the ventral fins, which 
are united to the anal fin, begin just behind the lower 
jaw. Both the dorsal and the anal fins cross over be- 
hind to the blind side, where their last rays form lobes 
which converge so sharply that the distance between 
the bases of the fins at this end is less than 2 / 3 (some- 
times less than 1 / 2 ) of the least depth of the tail. On 
the blind side these posterior rays extend beyond the 
base of the caudal tin; but on the eye side this arrange- 
ment produces a small, finless peduncle, the length of 
which is no more than about 1 j i of its depth. All the 
rays of the dorsal and anal fins are branched; but the 
ramification grows more pronounced posteriorly, the 
longest rays being most repeatedly branched, the last 
rays most deeply, the hindmost four or five right down 
to the base. The caudal fin is comparatively short, and 
sharply rounded at the hind margin. Both the ventral 
fins are united by a perfect fin-membrane to the first 
ray of the anal fin, and thus form an elongated, or 
rather, channel-like cup, open in front. In flic hind 
part of the bottom of this cup, just in front of the anal 
fin and almost at the middle of the ventral margin, we 
find the anal and genital openings, while the urethral 
papilla, as in most of these forms, lies on the eye side, 
beside the first ray of the anal fin. All the rays of the 
ventral fins are branched, the last rays most deeply, 
and even more than the first ray of the anal fin. The 
difference in size between the two ventral fins is in- 
considerable, that of the blind side being inserted only 
slightly, if at all, behind that of the eye side. The 
length of their base as well as their height varies be- 
tween about G % (on the blind side sometimes 5 1 2 %) 
and 7 % of the length of the body. The pectoral fin 
of the eye side is obliquely rounded, the fourth ray 
being the longest, but only slightly longer than the third. 
The two highest and the two lowest rays — sometimes 
only one on each side — are simple, the first ray very 
small, generally only V3 of the second, and closely 
united to the latter, and the eight middle rays are 
branched. The pectoral fin of the blind side is of al- 
most the same shape and structure, the only differences 
being that the fifth and sixth rays are the longest and 
generally equal in length, and that the rays are usually 
fewer, to which we may add that though the tin as a 
whole is shorter than the pectoral tin of the eye side, 
the first ray is as long as in the latter fin. The length 
of the pectoral fin of the eye side varies between about 
13 and 14 % of the length of the body, of the blind 
side between about 8 1 ,/ 2 and 1 0 1 / 2 % thereof. 
The Swedish name of Muller’s Topknot (luddkvarf = 
Hairy Fluke) is based on the name given the species by 
Abildgaard ( Pleuronectes kirtirs), and is derived from 
the singular structure of the scales. It is scarcely pos- 
sible for a fish fo be more thoroughly covered with 
scales than Muller’s Topknot is on the 'eye side. The 
whole body and head, the jaws and even the inter- 
maxillary bones, as far as they are exposed when the 
mouth is shut, and all the fin-rays are clothed on this 
side of the body with small but firmly attached, ctenoid 
scales. These scales are thin, in form semi-elliptical, 
with numerous, undulating grooves radiating towards 
the round, inserted end, and fine, circular strife eccen- 
trically arranged round the nucleus, which lies close to 
the truncate, posterior end. Only a narrow strip of the 
truncate part is left bare by the scale immediately in 
front, and this strip bears at the margin a transverse 
row of denticles, generally 8 or 9 (together with an 
inconstant number of extremely small ones). The den- 
ticles are set at right angles to the plane of the scale, 
conical, and pointed, and here and there on the body 
one of the middle ones is developed into a spine visible 
even to the naked eye. The surface of the eye side of 
