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Show 754 PROF. T. H. HUXLEY ON THE CLASSIFICATION [June 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 jiuviatilis, from the Arctic to the Black and Caspian Seas, another species, A. leptodactylus, ranges, associated with the allied but possibly distinct 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. Hagen3 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, oi 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 archipelagos4. 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 Germanos est, major silicet et simpliciter dictus Krebs vel Edelkrebs; eo enim minor est, et colore diversus qui saxatilis cognomiuatur Steinkrebs." ('Nomenclator Aquatilium,' p. 374). Heller (Die Crustaceen des siidlichen Europa, p. 217) refers our English Crayfish to this species; but no specimens I have seen agree with his diagnosis. Whether there is any difference 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 similar to these than to the form which is commonly known as A. fluviatilis on the Continent, is more than I a m 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 Flusskrebse :' (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. * I have been favoured by Sir Henry Barkly with the opportunity of examining 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-scbichte der Krabben und Krebse,' Band ii. p. 49) Herbst says :-" Dieser schdne Krebs halt sich auf den K a p in solchen Fliissen auf, die sich auf den Bergen befinden ; " and at the end he states, "die Fiisse haben insgesammt scheeren-lurmige Spitzen, da bey dem gemeinen Flusskrebs nur die ersten zwey Paarc dergleichen 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; aud therefore it must be concluded that his Cancer ca- |
