754 PROF. T. H. HUXLEY ON THE CLASSIFICATION [Julie 4, 



is known in the latter country as the " Steinkrebs," as a distinct 

 species, Astacus torrentium or A. saxatilis l . 



Eastward of the region inhabited by Astacus Jtuviatilis, from the 

 Arctic to the Black and Caspian Seas, another species, A. leptodac- 

 tylus, ranges, associated with the allied but possibly distiuct forms 

 A. pachypus and A. angulosus, in the southern part of the area ; 

 and it is remarkable that these Crayfishes not only frequent the 

 rivers which debouch into the Black Sea and the Caspian, but are said 

 to thrive in the salt waters of those seas. 



No Crayfishes are known in the Ob, Jenisei, Lena, or other rivers 

 which flow into the Arctic Ocean 2 ; but the Amur has one or two 

 species (A. dauricus). There is a species in Japan (A. japonicus) ; 

 and Dr. Hngen 3 enumerates no fewer than six species from British 

 Columbia, Oregon, and California. 



East of the Sierra Nevada, all the Crayfishes at present known 

 belong to the genus Cambarus, of which Dr. Hagen distinguishes as 

 many as thirty-two species. They extend from the Great Lakes to 

 Mexico, Guatemala, Cuba, and probably other of the West-India 

 Islands. Sloane, in his ' Natural History of Jamaica ' (vol. ii. 

 p. 271) describes two species in that island. According to the figure, 

 one of these attains a length of 12 inches. 



No Crayfishes are known to occur in the whole continent of 

 Africa, in Syria, the Euphrates valley, Persia, Hindostan, and India 

 beyond the Ganges, nor in China as far as the Corea, nor in the 

 Philippines, nor in any island of the Malay or Papuan archipelagos 4 . 

 The late Prof. Agassiz, though he sought for Crayfishes in the 



1 In 1560, Gesner was acquainted with this distinction : — " Astacus fluviatilis 

 talis apud Helvetios et Geruiauos est, major silicet et simpliciter dictus Krebs 

 vel ISdelkrebs ; eo enim minor est, et colore diversus qui saxatilis cognominatur 

 Steinkrebs." (' Nomenclator Aquatilium,' p, :J74). Heller (Die Crustaceen des 

 sudlichen Europa, p. 217) refers our English Crayfish to this species ; but no 

 specimens I have seen agree with his diagnosis. Whether there is any differ- 

 ence between A. saxatilis and the Crayfishes which have been named A. pallipes 

 and A. fontinalis by Lereboullet and Carbonnier ; and whether our English 

 Crayfish is more siindar to these than to the form which is commonly known 

 as A. fluviatilis on the Continent, is more than I am able to say at present. A 

 critical comparison of large series of specimens from different localities would 

 probably yield results of great interest to the theory of the origin of species. 



2 Kessler, " Die russischen Flusskreb.se " (Bull, de la Soc. Imp. des Nat. de 

 Moscou, 1874). 



3 ' Monograph of the North- American Astacida',' Illustrated Catalogue of 

 the Museum of Comparative Zoology at Harvard College, 1870. 



4 I have been favoured by Sir Henry Barkly with the opportunity of ex- 

 amining specimens of two kinds of " Cammarons," or so-called Crayfishes, from 

 the rivers of Mauritius. They are large Prawns. 



I must confess myself to be in a state of hopeless perplexity respecting the 

 Crayfish or Lobster which is said to occur at the Cape of Good Hope, Cancer 

 (Astacus) capensis of Herbst. At the beginning of his description (Naturge- 

 schichte der Krabben and Krebse,' Band ii. p. 49) Herbst says : — " Dieser schone 

 Krebs halt sich auf den Kap in solchen Fliissen auf, die sich auf den Bergen 

 befinden;" and at the end he states, "die Fiisse haben insgesammt seheeren- 

 formige Spitzen, da bey dem gemeinen Flusskrebs nur die ersten zwey Paare 

 dergleiehen haben." Moreover, the diagnosis runs, " pedibus omnibus cheli- 

 feris." It is impossible to suppose that Herbst should have made a mistake on 

 such a point as this; and therefore it must be concluded that his Cancer ca- 



