OP ARTS AND SCIENCES. 93 



the fact of authorship is not distinctly stated, but is gathered from the 

 context, or from subsequent works. 



Names of genera which contain no butterflies are introduced wherever 

 their members were originally considered as butterflies by the founder. 



With regard to the principles upon which this work has been under- 

 taken, I adopt, in general, those regarding genera enunciated by 

 Agassiz in the preface to his Nomenclator Zoologicus, and more re- 

 cently by Thorell, in his work on European Spiders, with such excep- 

 tions or modifications as are indicated in my canons of systematic 

 nomenclature.* There are, however, a few points which need special 

 mention. 



Only those names are introduced which are connected with the 

 binomial nomenclature founded by Linne : for this reason, the tri- 

 nomials of Iliibner and the terms applied by Linne himself to the 

 groups into which he divided Papilio, as well as the similar terms used 

 by other earlier writers, such as sorre of those of Fabricius, Ilerbst, 

 etc., have been totally disregarded. All, or nearly all, the trinomials 

 of Hiibner (used principally in the first volume of his Sammlung 

 Exotischer Schmetterlinge, and in his Systematisch-Alphabetisches 

 Verzeichniss) are actually used by him in some work or other (as in 

 the Tentamen or Franck's Catalogue) with a binomial application ; 

 and in those cases they are here introduced, but only dating from the 

 time at which and for the species for which they were employed 

 binomially. With regard to the so-called subgeneric appellations of 

 Linne and others, such as Plebeius, Nymphalis, etc., there are but two 

 views which, it seems to me, can consistently be taken of them : one, 

 that these authors always used them in a trinomial or quadrinomial 

 nomenclature, exactly similar to that of Iliibner, such as Papilio 

 Danaus candidus rapae, in which case they ought not to be adopted, or 

 else candidus should demand the same right as Danaus ; the other, that 

 they should be retained as names of groups exactly as they were first 

 used, at the head of divisions, in a plural form, Plebeii, Nymphales, 

 etc. Plural nouns as titles of groups, and singular nouns with a 

 generic signification, cannot be derived from one and the same source. 

 44 Noinina generica cum classium et ordinum naturalium nomenclaturis 

 communia, omittenda sunt." Now the early authors, in referring to 

 the true "genera" of Linne, always used them, as Linne* did, in a 

 singular form; but when referring to the groups into which Papilio 

 was divided, as groups, they always used them, as Linne did, in a 



* Amer. Journ. Sc. Arts [3], iii. 348. 



