Ml LLKR S TliPKNO'l'. 



459 



skin. The uiierculum and snbopercnluni rcscnil)]^ those 

 of tlie preceding;' species; l)ut the interopercnliini is still 

 nioi'e tajieriiiii" in front tlian in I'^kstrotn's Topknot, with 

 a distinct sinus in the lower margin, and also more 

 distant from the Io\\er ja.\\'. to the angular part of which 

 it is united l)y ligaments and I'ough skin. riie pre- 

 operculum is obtuse-angled, with a sinus in the iiind 

 margin just aliove the angle. The jaw-teeth in front 

 form a dense and tine card, 'i'lie palatal folds are \voll- 

 developed, l)ut in the upper jaw no broader than the 

 <ard of teeth, in the lower jaw still narrower. The gill- 

 rakers are set in a single row on the tirst branchial 

 arch, as in most of the liothhuc, I)ut are rather numer- 

 ous, about 2?) on this arch. The lower pharyngeals 

 are distincth' narrower tiian in Mkstrom s To|)knot and 

 without any marked ex])ausion for the patch of teeth: 

 they are furnished witli oid\- four or five rows of teeth, 

 pointed like tiie jaw-teeth but straight. 



The margin of the l)od\- is eutireh' surrounded 

 with tins, with the exception of the small sections oc- 

 cupied b^• tlie lower jaw, the intermaxillary bones, and 

 the extremely short peduncle of the tail. The dorsal 

 tin begins so far forward that its commencement, which 

 forms a lobe on the blind side, covers even the up])er 

 end of the maxillary bone; while the ventral tins, which 

 are united to the anal tin, begin just behind the lo^ver 

 jaw. Both the dorsal and the anal fins cross over be- 

 hind to the blind side, Avhere their last rays form lobes 

 \vhich converge so sharph' that the distance between 

 the bases of the fins at this end is less than '/g (some- 

 times less than ' j) of the least depth of the tail. On 

 the blind side these posterior rays extend beyond the 

 base of the caudal fin; but on the eve side this arrange- 

 ment produces a small, fitdess peduncle, the length of 

 wiiich is no more than about ' j of its depth. All the 

 rays of the dorsal and anal tins are l)i'anched; but the 

 ramification grows more pronounced posteriorly, the 

 longest rays being most repeatedh' 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 

 tins are united by a perfect tin-membrane to the tirst 

 ra^■ of the anal fin, and thus form an elongated, or 

 ratiier, channel-like cup, open in front. In the hind 

 part of the bottom of this cup. just in front of the anal 

 tin and almost at the middle of the ventral margin, Ave 

 find the anal and genital openings, while tlie urethral 

 papilla, as in most of these forms, lies on the eye side. 



beside the tirst ray of the anal tin. All tlie rays of the 

 \-entral tins are branched, the last rays most deeply, 

 and e\en more than the first ray of the anal fin. The 

 dift'erence in size between the two ventral fins is in- 

 considerable, that of the blind side being inserted only 

 slight h, if at all, behind that of the eye side. Th<f 

 lengtli of their base as well as their height varies be- 

 tween al)out (i % (on the blind side sometimes 5*2 %) 

 and 7 % of the length of the body. The pectoral fin 

 of tlie eve side is obliquely rounded, the fourtli i-:iy 

 being tlu; longest, but only slightly longer than tlie third. 

 The two highest and the two lowest rays — sometimes 

 onl\- one on each side — are simple, the first ray very 

 small, generally only '3 of the second, and closely 

 united to the latter, and the eight middle rays are 

 branched. The pectoral tin 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 fin of the eye side, 

 the first ray is as long as in the latter tin. The length 

 of the pectoral tin of the eye side varies between about 

 13 and \A % of the length of the body, of the blind 

 side between about 8V2 and 10\'2 % thereof. 



The Swedish name of Miiller's Topknot {luddhvarf = 

 Hairy Fluke) is liascd on the name given the species by 

 ABii-DGAAiii) {PJnironecfes huiiis), and is derived from 

 the singular structure of the scales. It is scarce!}^ pos- 

 sible for a fish to be more thoroughly covered with 

 scales than Miiller's Topknot is on the eye side. The 

 Avhole 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 tin-rays are clothed on this 

 side of the body with small but tirmly attached, ctenoid 

 scales. These scales are thin, in form seini-t'lliptical, 

 with numerous, undulating grooves radiating towards 

 the round, inserted end, and fine, circulai- stri;e 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 surfiice of the eve side of 



