ASTACUS. lol 



Sea and the Sea of Azov, and it is widely distributed in the Caspian Sea, 

 having been reported from the following points therein : Peninsula of Man- 

 ghishlak, Island of Cheleken, Krasnovodsk, Astrabad, Sara Island, Lenko- 

 ran, and Bakoo (Kessler, Eichwald). It has been taken with the dredge 

 from a depth of six to nineteen fathoms in the Caspian Sea (Kessler, p. 372). 

 I have seen specimens from the basin of the Danube as far up as Balaton 

 Lake * in Hungary (Coll. Peabody Mus. Yale Coll.), and Heller reports it 

 from the Theiss River and Mohacs. MiddendorfF states that it ascends the 

 Volga system to the sixtieth parallel, in the neighborhood of Tcherdy.t 

 It is also found to the northward in the rivers and lakes which drain into 

 the Baltic and White Sens, Erichson reporting it from Courland.J Kessler 

 from many of the lakes and rivers that connect with the Gulf of Finland ; 

 viz. Lakes Ilmen and Valdai, and the rivers Vodla, Vytegra, Sveer, Volkhov, 

 and Msta.§ Here it has invaded the domain of A. Jinviatilis. and according 

 to Kes.sler is supplanting that less fertile species.|| In the Northern Dwina 

 A. lepiodacti/lus alone is found, descending to Archangel.** 



The Ponto-Caspian basin is undoubtedly the original home of yl. leptodac- 

 ii/lus. Thence its migration into the northern rivers was made easy by the 

 canals connecting the Volga and Dnieper with the rivers of the Baltic and 

 White Seas. 



A. leptoilt(cff/lus was introduced by man in 1822 into the River Isset, a 

 tributary of the Tobol, in Western Siberia, and is now common in manv of 

 the streams of the Obi River basin, e. g. the Toora, Niza, Irtish, Tara, Om, 

 and also in the upper part of the Obi. Its distribution over such a wide area 

 of the Obi basin is due partly to spontaneous spreading, partly to artiOcial 

 transference from one stream to another. It is probable that crayfishes did 

 not exist in the waters east of the Ural Mountains until they were trans- 

 ported thither by man, although Pallas ft speaks of their presence in the 

 upper course of the Ui, an affluent of the Tobol, as early as 1770. As the 



* The water of Balaton Lake is said to be slisrlitly salt. 



t Sibirische Rcise, Bd. IV. Th. 2, p. 882, 1867. 



X Kessler {op. cii. ]). 253 [353]) dniibts wlietlier J. hptotlocti/lits be found in Courland, as Eriolisou 

 announced ; hut as the Soutl\ern Dwina is connected by means of canals with botli Lake Ilcuen and the Bcre- 

 sina Ilivcr (an affluent of tlie Dnieper), immigration of this species into Courland would be faeilitaled. 



§ Tlic Msta, which flows into Lake Ilmen, and thence through Lake Ladoga into the Gulf of Finlarid, is 

 connected by a canal with the Tvertsa, a tributary of the Volga. The Vytegra also communicates with the 

 basin of the Volga througli the Murinskoi Canal. 



II According to Kessler A. yptodacli/lits lays from 500 to 600 eggs, A. flmiatilis rarely more than 250. 

 ** A. leptmldcfi/hts is also found in Lapland, according to Gerstfeldt, op. cit., p. 589. 

 •f-j- Reise durch verscluedeue Provinzen des linssischeu Reichcs, Th. II. p. 381. 



