801 



tlie females between 14 and 1"), in the innles between 

 1.") anil 1 <i ". in relation to tiie doi'sal fin tlie\- lie so 

 till' li.irk that the distanee between their insertion and 



eo!nnion to both sexes, the males are distinguished at this 

 season by tiie nsual dermal eruption, consisting of small 

 round tubercles on the occiput, the opercula, the margins 



tlie tip of the snout is as a rule ])erceptil)ly more than i of the scales, and the inner surface of the paired fins. 



87 % (87' 3 — H4' o %) of tliat between the dorsal tin The Ziirtlie is pro|)erlv a marine fish, but also lives 



and the same point. j in the great lakes, and ascends i-ivers in order to spawn, 



The scales are niiildle-sized, deeply embedded in j being thus a so-called anadromous species. Its geo- 



the skin, and indirieated. Tliey are of an irreguiai' graphical range comprises Eastern Eurojie from Finland, 



(|uadrilateral siiape and rounded, with almost central , Sweden, North-western Germany, and the watershed of 



nucleus, dense concentric stri;e, and numerous and well- 

 defined radiating grooves, the latter alternating, both 

 in front (finer) and behind (coarser and more regular), 

 in their greater or less extent towai-ds the nucleus. 



In coloration two varieties are distinguished'', hlrk- 

 rimma (Pale Ziirthe) and srartriiiiiiia (Black Ziirtlie), 

 the latter being probablj- no more than the spawning 

 dress. Both on the head and the back the coloration 



the Danube to the Black Sea with its Itussian river 

 systems and the Sea of Azov. It makes its way up 

 the Elbe and Weser from the North Sea, but is want- 

 ing in the Ithine. In Finland, where it is common 

 among the southern islands and, to the east, in Lake 

 Ladoga, it does not go farther nortii, according to ]\1ela, 

 than the sixty-third degree, being very rare even in 

 that latitude. From the Swedish coast of the Gulf of 



is above blue or greenish brown, at the top of the sides j Bothnia we are told by Wide(;i!EN (1. c), though his 



of the body silvery ^\•ith a dash of blue, fading below 

 into the pure silvery white of the i)elly. On the sides 

 t)f the head the dark blue tint extends down to the 

 upper part of the gill-cover, and the silvery lustre 

 shows stronger or fainter traces of a brassA- colour. In 

 Germany its dark snout has gained for the Ziirthe the 

 name of Blaiinase or Bi(ssnase. All the fins are light, 

 gray or grayish blue, more or less tinged, especially 

 the caudal, with orange at the base. The iris is of a 

 pale brassy yellow, shading into greenish above the 

 pupil. (_)ur figure, -which is coloured from a sketch by 

 W. v. ^VRIG^T, represents the Ziirthe in this dress of 

 almost pure silver. On weedy bottoms or in dark 

 water the colours of the fish are greener with a more 

 powerful brass}- lustre. Siebold has described the dark 

 spawning dress, in which the sides of the body, even 

 below the lateral line and close to the ventral and anal 

 fins, acquire a singular silky lustre, this being caused 

 by a deep black pigment from ^vhich the ventral side 

 itself, from tiie lips to a narrow strip at the margin 

 behind the anal fin, stands off shnr[)lv -with its deep 

 orange hue. The latter colour also extends to the 

 paired fins and the base of the anal fin: the dorsal and 

 caudal fins, the upper margin of the pectoi'als, and the 

 lower margin of the anal fin being, on the other hand, 

 blackish. In addition to this spawning dress, which is 



statement is pei'haps questionable, that the Ziirthe oc- 

 curs in the lower course of the Lulea Elf (nearly 66° 

 N. lat.). The northernmost locality in Sweden to \\hich 

 we can with certainty assign this species, is the neigli- 

 bourhood of Hudiksvall (about 62° N.), from which 

 region Mr. WistkOm has sent to the Royal ^luseum a 

 specimen 24 cm. long, taken in the fjord of Lingaro 

 on one of the last days in September, 1882. In the 

 same neighbourhood, we are told, it sometimes, though 

 seldom, ascends tlie River Dekanger in spring. Ever 

 since NiLssos's time the Ziirthe has been known in 

 Blekinge; but in Scania it has never been found. It is 

 commonest in the 'Slnhv A'alley and tlie Baltic island- 

 l)elt with the streams that fail into this part of the 

 l>altic. In Lake Wener it is also found, and is some- 

 times caught, "especially in the months of May and 

 June" (Malm) in the River Gotha at Gothenburg. In 

 Norway, Denmark, and the west of th(! Baltic the spe- 

 cies is unknown; but from the Elbe it was described 

 even by Gesner and Schonevelde. From the Baltic 

 it enters the German Haffs to spawn. According to 

 Dybowski (1. c.) and Seidlitz'' it occurs in all the riv- 

 ers of the Baltic Provinces of Russia. Its Baltic range 

 being of such extent, we might well expect to find it 

 both oft" Gothland and Bornholm; but is has not yet 

 been observed in either of these localities. 



" Aci/orilinj; to Dyeowski tlie same sexual distinction was present in his specimens: but tlie percentages are somewliat lower, this 

 being probably due to a different manner of measurement. 



' According to Mr. Arosexius, who forwanled to the Eoyal Museum specimens of these varieties from the Motala River (Norrktiping) in 1834. 

 ■■ Fauna baltica, p. 101. 



