io FRANCIS HEMMING 



in 1934. In that volume the survey of the nomenclatorial issues arising in connec- 

 tion with the names of genera occurring in the Holarctic Region was combined with 

 a taxonomic appraisal of the status of the genera concerned. The generic names were 

 grouped under the families in which the genera concerned were currently placed, and 

 within each family were arranged in the systematic order then in general use. 

 Names that were invalid either under the Law of Homonymy or by reason of being 

 junior objective synonyms were cited immediately after the name accepted as the 

 oldest nomenclatorially available name applicable to the genus in question. To these 

 objective synonyms were added any generic names which, though available nomen- 

 clatorially, were then currently treated as junior subjective synonyms. An 

 arrangement of this kind is essential in any purely systematic check-list or catalogue, 

 but is now considered inappropriate in a work such as the present, the purpose of 

 which is purely nomenclatorial. Accordingly, in the present work the particulars 

 given for each generic name are exclusively nomenclatorial in character. The only 

 comment offered in supplement to the necessary bibliographical particulars is in 

 respect of those cases in which a generic name is objectively invalid under the Code 

 and in consequence could not in any circumstances be validly employed. The 

 exclusion of subjective ideas regarding the taxonomic relationship towards one 

 another of the genera bearing the names listed has made it possible to simplify the 

 presentation of the whole subject by arranging the whole body of generic names in a 

 single alphabetical list. 



The fact that the information now provided in relation to generic names is con- 

 fined entirely to matters of objective nomenclatorial fact greatly enhances the value 

 of the present work as a guide to the nomenclature of the genera of the butterflies. 

 This does not do away with the need for a synonymic check list of the butterflies of 

 the world ; it is only a step towards the preparation of one. 



(c) Determination of the taxa represented by nominal species which are the type-species 

 of genera 

 Many genera, especially those of older date, have as their type-species nominal 

 species bearing names which are commonly treated as junior subjective synonyms of 

 other names and are themselves practically unknown, except to specialists. Accord- 

 ingly, in order to make clear the meaning of the entries made in respect of such 

 names, brief notes have been added setting out the synonymy currently accepted for 

 the names of the type-species concerned. These notes, which have been inserted by 

 way of explanation only, have been kept entirely distinct from the entry made for the 

 generic name itself, this latter, like all similar entries, being confined to the recording 

 of the relevant objective nomenclatorial facts. 



IV. COLLECTION OF THE INFORMATION 



The information needed for the preparation of the present work was of three kinds. 

 First, it was necessary to build up as complete as possible a list of the names so far 

 published for genera of butterflies, and to ascertain by whom, when and in what 



