148 A REVISION OF THE ASTACIDA. 
In 1858 Lereboullet clearly pomted out the differences between the 
three species of Astacus inhabiting Western and Central Europe, viz. A. jlu- 
vialilis, A. pallipes (Dohlenkrebs), and A. dongicornis (Steinkrebs). Lereboullet’s 
A. longicornis is the species previously described by Schrank as Cuncer tor- 
rentium. 
In 1859 there was published a revision of the European Astaci by Gerst- 
feldt,* based chiefly upon the material m the Museum of the Imperial Acad- 
emy of Sciences of St. Petersburg, and in the collection of the University of 
Dorpat. Gerstfeldt concludes that there are only two species of Astacus in 
Europe: A. fuviaiilis (including four varieties, A. fluviatilis communis, A. lepto- 
dactylus Eschscholtz, A. angulosus Rathke, and A. pachypus Rathke) and A. tor- 
reutium, the “ Steinkrebs.” No one will deny that A. fluviatilis, leptodactylus, 
and pachypus are closely related to each other, but, judging from the mate- 
rial which I have exammed, they constitute three species. It is true that 
some specimens of A. fuvialilis vary slightly in the direction of A. deptodac- 
fylus,t and vice versa, but not to such a degree as to bridge over the chasm 
between the two forms, or to puzzle even an untrained eye in separating 
them. I agree with Kessler in considering A. juviatilis, leptodactylus, and 
pachypus to be distinct species. A. angulosus, on the other hand, appears 
to pass by transitional forms into A. /eptodactylus, and may be considered a 
local variety of the latter. Gerstfeldt’s knowledge of the “Steinkrebs ” was 
limited to five poorly preserved specimens from the Rhone River, which 
his description on page 577 shows to have been A. pallipes Lereb. He con- 
founds this form with another species, the Cancer torrentium of Schrank. 
Distribution. — Owing to the lack of discrimination on the part of most 
authors between the three species A. fluviatilis, pallipes, and torrentium, it is 
impossible accurately to determine the geographical range of these common 
European crayfishes, and the problem is further complicated by the artificial 
introduction of these animals as a food supply into many rivers to which 
they are not indigenous. A, fevatilis alone among them is found within the 
limits of the Russian Empire. “ Here it inhabits especially the Baltic water- 
shed, where it reaches the northern as well as the eastern limit of its dis- 
* Ueber die Flusskrebse Buropa’s. Von G. Gerstfeldt. Mém. Acad. Impér, Sci. St. Pétersbourg, 
Tom. IX. 
+ For example, in some specimens of 4. fluviatilis the margins of the rostrum are slightly deuticulate, 
and the fingers are longer than in the ordinary specimens. 
} Kessler (op. cit., p. 868) points out the fact, that in the Baltic area, where 4. leptodactylus has invaded 
the domain of 4. fluviatilis, no intercrossing of the two forms has taken place, but the former is driving out 
the latter. 
