664 PROCEEDINGS OF THE NATIONAL MUSEUM. vol xx. 



tion was inoperative, because be bad been forestalled by an earlier 

 writer. J. C. Fabricius, in bis various writings, of wbicb it will be 

 sufficient to cite tbe 'Species Insectorum,' 1781, and the ' Entomologia 

 Systematica,' 1793, consistently places Astacus marinus (Cancer gam- 

 marus Linnaeus) as tbe first species of tbe genus Astacus, giving to 

 A. fiiiviat'dis invariably the second place. There can therefore be no 

 reasonable gainsaying tbat he made the European lobster, and not 

 the river crayfish, the type. From this it follows * * * that the 

 generic name of the lobster is properly Astacus, and that of the Euro- 

 pean crayfish Potamobius." 



It is hard to believe that this contention of Mr. Stebbing's is made 

 in good faith, involving as it does an unreasonable and long-discarded 

 method of ascertaining a type. Such a method is repudiated every time 

 we concede to an author who first subdivides a genus in which no type 

 has been specified, the right to restrict the original name to such part 

 of it as he pleases. It is not true that the first species is presumably 

 the author's implied type. Fabricius's genus Astacus was formed by a 

 dismemberment of the genus Cancer of Linnaeus, and the sequence of 

 the two species under consideration in Fabricius's works was undoubt- 

 edly derived from the " Systema Naturae," where (in the twelfth edition) 

 Cancer gammarus stands as No. 62, Cancer astacus as No. 63, in the 

 genus Cancer. A better, though not a valid, claim might be set up for 

 A. jiumatilis as Fabricius's implied type of his genus Astacus, since 

 that species is the Cancer astacus of Linnaeus. 



In Agassiz's '-'Nomenclator Zoologicus" the name Potamobius is 

 entered as a genus of Brachyura, with a citation of Leach's article in 

 "Dictionnaire des Sciences Naturelles," XII, 1818. By reference to 

 this work it appears that the name occurs on page 75, under the Galli- 

 cized form " Potamobie," in a merely nominal, alphabetical list of the 

 genera of Crustacea. Since the crayfish and lobster are both entered 

 elsewhere in the same list, by the names of " Ecrevisse" and " Homard," 

 I am inclined to think that u Potamobie" was here really intended for a 

 genus of fiuviatile crabs, as assumed in the " Nomenclator," and that it 

 was written through a lapsus pennce for " Potamophile," i. e., Potamo- 

 pliilus or Potamon. As the name occurs as a pure nomen nudum in the 

 "Dictionnaire," it would be unworthy of notice but for the fact that 

 Desmarest said in 1823 1 1 "II est probable que ce genre [Thelphusa ou 

 Potamophilus] diff ere peu, ou ne diff ere pas de ceux qui ont ete nommes 

 Potamon par M. Savigny, et Potamobia par M. Leach," and that Risso 

 in 1826 2 adopted " Potamobius Leach" (with "Potamophile" as the 

 French equivalent) as the generic name for the fresh water crab, Potamon 

 fiuviatilis. In this way, probably, it came to pass that Huxley 3 was 

 led into the essentially erroneous assertion that Potamobius had been 

 used in another sense before it was applied to the crayfish. 



1 Dictionnaire des Sciences Naturelles, XXVIII, p. 246. 

 2 Hist. Nat. de l'Europe Mend., V, p. 14. 

 3 Proc. Zool. Soc. London, 1878, p. 752. 



