ASTACUS. 15 
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, Kichwald). 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 Seas, Erichson reporting it from Courland,t 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. fiuviatilis, and according 
to Kessler is supplanting that less fertile species.|| In the Northern Dwina 
A, leptodactylus alone is found, descending to Archangel.** 
The Ponto-Caspian basin is undoubtedly the original home of A. deptodac- 
tylus. 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. leptodactylus was introduced by man in 1822 into the River Isset, a 
tributary of the Tobol, in Western Siberia, and is now common in many 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 artificial 
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 ++ 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 slightly salt. 
+ Sibirische Reise, Bd. IV. Th. 2, p. 882, 1867. 
+ Kessler (op. cit. p. 253 [353]) doubts whether 4. lepfodactylus be found in Courland, as Mrichson 
announced; but as the Southern Dwina is connected by means of canals with both Lake Ilmen and the Bere- 
sina River (an affluent of the Dnieper), immigration of this species into Courland would be facilitated. 
§ The Msta, which flows into Lake Ilmen, and thence through Lake Ladoga into the Gulf of Finland, is 
connected by a canal with the Tvertsa, a tributary of the Volga. The Vytegra also communicates with the 
basin of the Volga through the Murinskoi Canal. 
|| According to Kessler 4. leptodactylus lays from 500 to 600 eggs, A. fluviatilis rarely more than 250. 
** 4. leptodactylus is also found in Lapland, according to Gerstfeldt, op. cit., p. 589. 
+} Reise durch verschiedene Provinzen des Russischen Reiches, ‘Th, IL. p. 381. 
