SAl.MONID.K. 



891 



Cknus coregonus. 



All till' ti'iili iif tin- miiKtIi, cxce/if those on the Ioik/iii-, (!■•< a nilr soon (lis(i/)/>riniiii/ <li(iiiiii i/iiiiiili. or soon con- 

 cealed ill fill' !/ii»is, or jx-rsisfeiif as srottercil, Jiiic, rilliforiii, moliilf tcctli, or ciit/rrli/ iraiitiiii/. Leiujth of the 

 maxUliiries .'>() {exceptionally 52) — S2 %, and of the loa-er jair 7 {except lotiall if 74) — 4!) %, uf tJiaf of the lif((d 

 reduced, lireadth of the snout across llic artiodar kiiahs uf the maxillaries perceptibli/ less than that of the i)i- 

 tennliital s/iair. a-hich is at least ' , ((■xcciit/niiidlji :> } "„) of the Innitli if thf hiiiil. Ilasc if the dorsal Jin less 

 than I') "« of the Icnijth of tlw IkhIi/, tint more than Indf the lcn(/th if the head rcdarcd. J'l/loric appendages 

 a-ell-dereloped. Scales middle-sizeil, alioiit s(l — <.)() {exceptinnall/i ahnat Id — 111)) in the laterrd line, 



a-hiih is loin/defe. 



Till- dental rcdurtiun wliit'h we have svvu in tlie 

 preceding _u'enera — in the strength of the teeth in 

 Mallotus, and hoth in tlieir strength and nuniher in 

 Thijmallus — has advanced still further in the I i\\ yniad 

 genus {('oreqonas) towards the Cvjjrinoid t\[)e. The 

 direction of the reduction is indeed not the same as 

 in Thijmallus, the teeth on the tongue being persistent, 

 and sometimes even more developed than in ^fallotus. 

 But else the rediictiijn is a continuation of that which 

 we have seen in Thi/niallas, and in tlii'ii' form, the 

 jaw-teeth, where they are present, come nearest to 

 those of the Graylings. The maxillaries and the vomer 

 are alwavs toothless in Coregonus ; but on the inner 

 (hind) surface of the intermaxillaries and on the an- 

 terioi- |)art of the palatines the Gwvniads proper are 

 usunli\' furnislied with teeth, on the former liones set in 

 a thin transverse row and mobile as in JIagil, on the 

 latter firm and pointed, but small. Among the true 

 Gwvniads we find onlv dermal papiihe instead of teetli 

 in the lower jaw; but among the \ endaces small teeth 

 sometimes occur in the anterior part of the lower jaw, 

 as well as on the intermaxillaries". In tlie i)liar\nx, 

 however, we find teeth, numerous thougii small, not 

 onlv on the so-called pharyngeals, but also on the 

 upper parts of the posterior branchial arches''. 



The reduction of the teeth is partly compensated, 

 as u>ual, \i\ the apparatus composed of the gill-rakers 

 (fig. 222), wiiich are subject in Coregonus to gr<'at 

 variations, ])robabh- connected with variations in tlie 

 diet of these fishes. The rule is apparently that, where 

 the diet consists of large objects, ])rincipally fish, the 



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,#5*.-^- 





. On^N'S^'^T^^ 



,;5^^;2^^*'^ 



XA*»^^iiSj^ 



^ 



Fig. 'i'J-i. A, gill-rakers (46) ami Lirancliial laiiiell* on tlie first left 



branchial arch in a Vendace {Core- 



ijonus albula). 

 B. ., (60) on the first left branchial arch in a 



Pelei (Coregonus cyprinoides). 

 ('. (4.'i) on the first left branchial arch in an 



.\.<p-Gwymad {Coregonus aspius). 

 /I. ., CJTJlon the first left branchial arch in a 



E. ., fi,'!)! fiwyniad {Coregonus liiviiretiis). 



F. .. ("20) on the first left branchial arch in a 



Polcnr {Coregonus polcur). 

 Figs. B — F .ifter WinF.niiKX. 



Smit'I'. 1. c., t;ib. loetr. VIII. (Jongoni, note to S|ieiMnicii No. 5. 

 See above, p. 5'2:i, note a. 



