rnci' (iC the 



,vh<ilr ii'i^. I'liI l)r(i;Hlcst ;it tlic aiilci'lcir 

 eve. 'I'lir |Hi|iil is t'aii'h' circul;!!', will 



I an"'l<' '" li'diit. In ;idult \ eiidiU'c the eves (iccu|n' \\itli 

 fair extU'tiu'ss the second (luarli'r of llie Icnixdi of tlic 



I head, ihonuli tlic unterior corner of tlic eye encfoachcs 

 niidii tlic first i|nartcr thereof, the average long'itudin;il 

 (liriiiietcr of tlic e\c lieing thus about 2') '^i/' of the 

 k'liii'th of the head, lint the length of the siioiit oiih' 



i about 'iV ., ''/ of the same. The Acrtical dianielcr is 



\ soiuc\vliat less, in uUmUt on an aNcrage .■iliont 2M '»'', in 

 r\mha 'I'l^ ., "», of the length of the head. The hrcidth 

 of the intcrorhital Sj)ace, which rises only a little alioxc 

 the uji|icr margin of the eves, is in (ilhula idioni ci|nal 

 to till' longitudinal diameter of the c^■es', in r'niilia 

 somewhat greater'. The ax'erage hi'cadth of the snout 

 across the articular kiiohs of the maxillaries is 111 '-'-v of 

 the length oi' tlie head. Tlic two nostrils on each side 

 of the snout arc situated as in the jircceding s])ecies, 

 somewhat nearer to the orbit than to the tip of tlie 

 snout. The hind margin of the anterior nostril is raised 

 in the form of an oblicjueh- cut tulie; the |)ostcrior 

 nosti'il. ^^■hicll is larger, mar be closed from in front 

 by means of a semicircular dermal flaii. The maxillaries 

 — as they appear externally — ai-e of uniform breadth, 

 curved like a sabre, and bluntly rounded at the hind 

 extrcmitx'. Their a\crage length from the toji of the 

 articular processes is in alh/iJa about ;>.') %. in rinihii 

 about o4 %. of that of tlic licad, or in tlie former about 

 48 ".., ill till- latter about 4.') %, of that of the head 

 reduced. Thcii- breadth is on an average ' ., of their 

 length. Tlieir supplcmentarA" (jugal) bone is similar in 

 shape to their lateral part and nearly ^i^ of its length, 

 being elongated to a point in front. The average length 

 of the lower jaw is in aUiula about hi %, in riinhii 

 about 411 %. of that of the iiead, or in the former aljoiit 

 70 %, in the latter about GO "«, of that of the head re- 

 duced. The dentition of the mouth and the gill-rakers 

 (41 — 48, exce|)tionally .HVI or even 38) we have already 

 noticed. The transverse palatal folds (vela) are well- 

 developed, especially in the lower jaw. The gill-open- 

 ings extend along about the hist third of the upper 

 operculai- mai-gin and down to about a line with the 



\CK. 895 



anterior margin of the eye, to Avhich point the bran- 

 chiostcgal membranes are free; both from each other and 

 the isthmus, though tlie\- cross at the extreme fr<int, 

 in the same manner as in the preceding genera. The 

 branchiostegal ra\s arc thin and flat, more or less cur- 

 ved ill a sabre-like form. The operculum is obliquely 

 ipiadraiigiiiar, with the lower anterior e<)rner incst 

 pointed and most tdongateil. Mack from the articidar 

 jirocess runs a ridge, fainth' marked in the bone itself, 

 but more distinctly indicalcfl bv a darker colour. Within 

 the right angle of the preoperculura lies a poi'e, marked 

 b\ a darker colour, and belonging to the inner osseous 

 ridge of the prc^ipcrcnlum, which ridge it piei'ces, but 

 eo\-crcd hx I lie adipose membrane that liere. as usual, 

 coNcrs the ramifications of the lateral line. This jjore 

 is alwa\s distinct in Scandinavian \ endace and gene- 

 rally in young Gwynia.ds (as in young Xelmas); but in 

 adult specimens of the largei' Coreffoni (as in the Nehna) 

 it Ijecomes more and more indistinct, usually invisible. 



The dorsal fin is of the sha])e commonest among 

 the .^salmonoids, trajie/.oidal, the first branched ray being 

 the longest in the tin. The distance between it and the 

 tip of the snout'' is on an average about 43'/., % of the 

 length of the body, usual!}' somewhat greater than in 

 the closely allied Siberian form Coregonus MerkiL The 

 base of the fin measures on an average in aJbtila about 

 '.( "„, in riiiiha about 10 %. of the length of the body, 

 and its height (the length of the longest ray) in the 

 former about 14 %, in the latter about 15 % of the same. 

 The anal tin differs but little from the dorsal, but is 

 longer and lower, most so in rimliii. its base measuring 

 on an average about 11 or \'2 "«, its height about 8' ,, 

 — -9' 2 %, of the length of the body. Its distance from 

 the ti]i of the snout is on an average 69' ^, '■'a oi' the 

 length of the bodw It terminates, like the adipose fin, 

 at a distance from the caudal tin that is on an average 

 Vi„ of the length of the body. The caudal fin is deeply 

 forked, most so in vlmba, the average length of the 

 middle rays being about 5'\,— 5 %, of the longest rays 

 about 17 — 19 ?», of the length of the body. 



The ]iectoral tins are obliquely pointed, and their 

 leno'tli is on an averatre 1 (> — 15 % of that of the bod\'. 



larv bo 



The changes of growth nm between about .T2 .niiil 2i) %. 



The changes of growth run between abont 27 iniil '20 %. 



On an average 25'7 'i of the length of flic head. 



On an average 277 °o of tlie length of the head. 



\ye may reiniml the reader that here, as in llie fulhiwing Gwvniods. the snonl is nieasiired from the articular knob of llie inaxil- 



iiflintinn,, Fishes. 113 



