9(12 



SC A N 1 ) I N A \' I A N V 1 .S 1 1 K S . 



mens — and dci^ii-Miuiitcd {li/ipsehirhi/iiflii"), ov I)et\\ccii 

 narrow-snouted {sfenorlif/i/cli)'') and liroad-snuiited (ciiri/- 

 rlii/iiclii'), without these diti'ei-eiices being always at- 

 tended l)v analogous differences between dense gill- 

 rakers {p>/rnoceiifrl'') and scattei'cd {iimiiofeiitr/'). To 

 this we must add tliat among the comparatively pyc- 

 nocentrous Gwvniads of Lake Welter specimens occur 

 (tig. 22(1) Aviiich dilVci- in hai-(il\- an\' respect from the 

 form of the nianoeenl imils (iw\iiiads, e. g. in Lake Stor 

 (tig. 22.")). All examiiiatiun (if (he Lake Wener (iwyn- 

 iads has yielded the same result: Imr in both the.se 

 lakes, as well as in tlie sea and in the large rivers 

 flowing into the sea. there apjiears a still more pro- 

 minent alteration in the firm of the snout, an alteration 

 which has given rise to the name of ndhhsik {Beaked 

 (iiriiii'idil. Houting: hg. 227), the o.ii/iiii/tirhuf: oi' old 

 writers. This alteration consists partly in the prolonga- 

 tion and thickening of the ethmoiflal cartilage, but 

 mainly in an agglomeration of cotuiective tissue and 



tiieir \arving degrees of resemblance to one or other 

 of the above-mentioned extremes, the iiiiih-siui and the 

 pdlciir. 



The shape of tlie snout also affects the length of 

 the jaAvs, from which we mav dei'i\e important cha- 

 racters. The appearance of the form-series at once 

 suggests that the ])ycnocentrous forms should have longer 

 jaws, and the changes of growth'' sIkjw that during 

 youlli the relati\e lengtli of the jaws undergoes a re- 

 duction. Hut in old (Twyniads from Lake W'ener — the 

 form which in (u'ntheh bears the name of ('(ircr/ovus 

 ma.riUariii, the German Madiri-Maraiic — \ve observe 

 a retrogression towards the characters of youth, a re- 

 trogression which ranges this form, as regards the 

 length of the maxillaries, even when the tip of the 

 snout is prolongated to the Houting type {('or. axi/- 

 r]n/iicliit»), beside the |)vcnoceiitroiis nf<ji from Lajjland. 

 The other extreme of the series — the jinjciir form, 

 which, as we have mentioned, really belongs to .Silieria 



fat. It is analogous to the elongation of the point of : and Northern Russia, but also occurs in the northern- 



tlie lower ja^\• in the Salmons, and cannot in itself 

 justify any sjiecitic distinction, whether it appears in 

 the narrow-snouted Gwyniads-^ or in the l)road-snouted". 

 Its reaches its highest development in old (Iwytiiads 

 from the depths of Lake Wener, which do not differ, 

 however, in other resjiects from theii' eompanious, tlie 

 broad-snouted (Twyniads of tiie same lake. l>iit the 

 Houting form was first observed in the Nortli Sea on 

 the lielgian. l*uteli, and (iermaii coasts, whence it ascends 

 the Khine, Weser, and Fdlie in order to s]iawn, and in 

 the soutli of the llaltie. wliere it enters tlie Haff's and 

 the Oder. 



However variable the sha| f the snout \\v,\\ a])- 



])ear, it is still the most trustworthy guide to the de- 

 termination of the forms — as the fisherman's experience 

 has long since taught him — although the characters 

 eaiuiot be well defined. This indefiniteness of-'character 

 we can easih' uiidei'staiid, tor we can range the diff'e- 



most ri\ers of Sweden — sometimes has the maxillaries 

 so reduced that we have conferred on this modification 

 the special name of lir((']ii/iiii/fit(i.r'. 



The shape of the body is the same as in the \"en- 

 dace, Ijiit in general somewhat deeper, dee]iest as a 

 ruk' in the jKilcur and the forms that come nearest it, 

 the manocentrous forms as a I'ule having a deeper body 

 than the pycnocentrous. The greatest depth of the 

 body varies in adult Gwyniads between about 22 and 

 25 % (in gravid females as much as 27 %) of its length; 

 in the polnir tlie percentage is usually 2(3 or 27. In 

 young (iwyniads measuring 37 — 143 mm. we find the 

 greatest depth to increase with growth from L5' ^, to 

 lil'/o of the length. But on account of the temporary 

 variations due to the periodical tumidity of the gene- 

 rative organs, the greatest dejith of the body, here as 

 in most cases, is ill adapted to express its characteristic 

 form. Far more ini)iortant in this respect is the least 



rent forms in an almost unbroken series according to ' depth of the l)ody. This is seldom so small as in the 



" rifjriXog, high. 



' arevog, narrow. 



' etQig, broad. 



'' From 7Cl.'X)'oc, dense, and y.iriQOV, s/iine. 



' /.lavog, scattered. 



f Smitt. 1. c. tafl. IV. tigs- •;'■' and 70. 



1 1. c, tig. 67. 



'' 1. c, tab. nic-tr. XIII, ''/* and ' ,, in Nos. 36-2—364 and 397—403. 



'' Answering in essential respects ti. a form wlncli inliabils tlie depths of tlie Lake of Constance, and whicli lias been named t'ore- 

 ijoniis aeronhis. But this latter form, judging l.y tlie two specimens we have examined (see Smitt, 1. c., tab. metr. X, Nos. 11)2 and 163), 

 lias mucli longer pectoral and ventral fins and a shorter snout. 



