6()4 PBOCEEDIXGS OF THE XATTOXAL MUSEUM. 



tion was inoperative, because lie had been forestalled by an earlier 

 writer. J. C. Fabricius, in his various writings, of which it wjII be 

 sufficient to cite the 'bpecies Tnsectoruni,' 1781, and the 'Entomologia 

 Systematica,' 1793, consistently places Asfacus marinna {Cancer f/am- 

 mnriis Linnaius) as the first species of the genus Astacu.s, giving to 

 A. ^fluviatilis inviirinhly the second place. There can therefore be no 

 reasonable gainsaying that 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 Astocws, and that of the Euro- 

 pean crayfish PotamohiHsy 



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

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

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

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

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

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

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

 dismemberment of the genus Cancer of Liuuii-us, and the sequence of 

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

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

 Cancer gammarus stands as No. 02, Cancer astacus as No. 03, in the 

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

 A. fuvtatilis 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 Potanwbius 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 " Potamobie" was here really intended for a 

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

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

 pJiilus 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:' "II est probable que ce genre [Thelphusa on 

 PotamopMlus] diff ere peu, on ne difi'ere pas de ceux qui ont etc nommes 

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

 in 1820- adopted ^^ Potamobius Leach" (with "Potamophile" as the 

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

 fiutnatilis. In this way, probably, it came to pass that Huxley-^ 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 rEniope Morid., V, p. 14. 

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



