148 A EEVISION OF THE ASTACID.E. 



In 1858 Lereboullet clearly pointed out the differences between the 

 three species of Astacus inhabiting Western and Central Europe, viz. A.flu- 

 viatilis, A. pallqyes (Dohlenkrebs), and A. longicornis (Steinkrebs). Lereboullet's 

 A. loiigicornis is the species previously described by Schrank as Cancer tor- 

 rent lum. 



In 1859 there was published a revision of the European Astaci by Gerst- 

 feldt,* based chiefly upon the material in 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. fltiviatUis (including four varieties, A.fluviatilis comimmis, A. lopio- 

 dactylm Eschscholtz, A. angulosus Rathke, and A. pachypus Rathkej and .4. tor- 

 re)dium, the "Steinkrebs." No one will deny ihnt A. Jtiiviatilis, leptodadylus, 

 and pachypus are closely related to each other, but, judging from the mate- 

 rial which I have examined, they constitute three species. It is true that 

 some specimens of A. fuviatilis vary slightly in the direction of A. Icptodac- 

 tyliis,^ and vice versa, but not to such a degree as to bridge over the chasm 

 between the two forms, or to puzzle even an imtrained eye in separating 

 tliem. I agree with Kessler in considering A. fuviatilis, leptodacti/lus, and 

 pachypus to be distinct species. J A. auynlosns, on the other hand, appears 

 to pass by transitional forms into A. leptodactylus, 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 torrentimn of Schrank. 



Distribution. — Owing to the lack of discrimination on the part of most 

 authors between the three species A. fluviaiilis, pallipes, and iorrentium, 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 man\- rivers to which 

 they are not indigenous. A.fluviatilis 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 Europa's. Von G. Gerstfeldt. Mem. Acad. Imper. Sci. St. Petersbourg, 

 Tom. IX. 



f For example, in some specimens of A.fiivid/iUs tlie margins of the rostrum are slightly dcntieulate, 

 and the fingers are longer than in the ordinary specimens. 



+ Kessler (np. cit., p. 368) points out the fact, that in the Baltic area, where A. leptodactylus has invaded 

 the domain of A.fluviatilis, no intercrossing of the two forms has taken place, but the former is driving out 

 the latter. 



