As I have already remarked, the very numerous {298} specimens of English and Irish crayfishes which have passed through my hands, have all presented the character of Astacus torrentium, with which also the description given in works of recognised authority coincides as far as it goes.[21] The same form is found in many parts of France, as far south as the Pyrenees, and it is met with as far east as Alsace and Switzerland. I have recently[22] been enabled, by the kindness of Dr. Bolivar, of Madrid, who sent me a number of crayfishes from the neighbourhood of that city, to satisfy myself that the Spanish peninsula contains crayfishes altogether similar to those of Britain, except that the subrostral spine is less developed. Further, I have no doubt that Dr. Heller[23] is right in his identification of the English crayfish with a form which he describes under the name of A. saxatilis. He says that it is especially abundant in Southern Europe, and that it occurs in Greece, in Dalmatia, in the islands of Cherso and Veglia, at Trieste, in the Lago di Garda, and at Genoa. Further, Astacus torrentium appears to be widely distributed in North Germany. The eastern limit of this crayfish is uncertain; but, according to Kessler,[24] it does not occur within the limits of the Russian empire. {299}
[21] See Bell. “British Stalk-eyed Crustacea,” p. 237.
[22] Since the statement respecting the occurrence of crayfishes in Spain on p. 44 was printed.
[23] “Die Crustaceen des Südlichen Europas,” 1863.
[24] “Die Russischen Flusskrebse.” Bulletin de la Société Impériale des Naturalistes de Moscow, 1874.
Astacus torrentium appears to be particularly addicted to rapid highland streams and the turbid pools which they feed.
Astacus nobilis is indigenous to France, Germany, and the Italian peninsula. It is said to be found at Nice and at Barcelona, though I cannot hear of it elsewhere in Spain. Its south-eastern limit appears to be the Lake of Zirknitz, in Carniola, not far from the famous caves of Adelsberg. It is not known in Dalmatia, in Turkey, nor in Greece. In the Russian empire, according to Kessler, this crayfish chiefly inhabits the watershed of the Baltic. The northern limit of its distribution lies between Christianstad, in the Gulf of Bothnia (62° 16′ N), and Serdobol, at the northern end of Lake Ladoga. “Eastward of Lake Ladoga it is found in the Uslanka, a tributary of the Swir. It appears to be the only crayfish which exists in the waters which flow from the south into the Gulf of Finland and into the Baltic; except in those streams and lakes which have been artificially connected with the Volga, and in which it is partially replaced by A. leptodactylus.” It still inhabits the Lakes of Beresai and Bologoe, as well as the affluents of the Msta and the Wolchow; and it is met with in affluents of the Dnieper, as far as Mohilew. Astacus nobilis is also found in Denmark and Southern Sweden; but, in the latter country, its introduction appears to have been artificial. This crayfish is said occasionally to be met with on the Livonian coast in the waters of the Baltic, which, however, it must {300} be remembered, are much less salt than ordinary sea water.
It will be observed that while the two forms, A. torrentium and A. nobilis, are intermixed over a large part of Central Europe, A. torrentium has a wider north-westward, south-westward, and south-eastward extension, being the sole occupant of Britain, and apparently of the greater part of Spain and of Greece. On the other hand, in the northern and eastern parts of Central Europe, A. nobilis appears to exist alone.
Further to the east, a new form, Astacus leptodactylus (fig. [75]), makes its appearance. Whether A. leptodactylus exists in the upper waters of the Danube, does not appear, but in the lower Danube and in the Theiss it is the dominant, if not the exclusive, crayfish. From hence it extends through all the rivers which flow into the Black, Azov, and Caspian Seas, from Bessarabia and Podolia on the west, to the Ural mountains on the east. In fact, the natural habitat of this crayfish appears to be the watershed of the Pontocaspian area, excluding that part of the Black Sea which lies southward of the Caucasus on the one hand, and of the mouths of the Danube on the other.[25]
[25] These statements rest on the authority of Kessler and Gerstfeldt, in their memoirs already cited.