RULES OF ZOOLOGICAL NOMENCLATURE. 33 



§ 8. If the later name be so denned as to be equal in extent to two or 

 more previously published genera, it must be cancelled in toto. 



Example. — Psarocolius, Wagl. 1827, is equivalent to five or six genera 

 previously published under other names, therefore Psarocolius should be 

 cancelled. 



If these previously published genera be separately adopted (as is the case 

 with the equivalents of Psarocolius), their original names will of course 

 prevail ; but if we follow the later author in combining them into one, the 

 following rule is necessary : — 



\_A genus compounded of two or more previously proposed genera ivlwse cha- 

 racters are now deemed insufficient, should retain the name of one of them.~] 



It sometimes happens that the progress of science requires two or more 

 genera, founded on insufficient or erroneous characters, to be combined toge- 

 ther into one. In such cases the law of priority forbids us to cancel all the 

 original names and impose a new one on this compound genus. We must 

 therefore select some one species as a type or example, and give the generic 

 name which it formerly bore to the whole group now formed. If these 

 original generic names differ in date, the oldest one should be the one 

 adopted. 



§ 9. In compounding a genus out of several smaller ones, the earliest of 

 them, if otherwise objectionable, should be selected, and its former generic 

 name be extended over the new genus so compounded. 



Example. — The genera Accentor and Prunella of Vieillot not being consi- 

 dered sufficiently distinct in character, are now united under the general 

 name of Accentor, that being the earliest. 



We now proceed to point out those few cases which form exceptions to the 

 law of priority, and in which it becomes both justifiable and necessary to 

 alter the names originally imposed by authors. 



\_A name should be changed ivhen previously applied to another group ivhich 



still retains it.~\ 



It being essential to the binomial method to indicate objects in natural 

 history by means of two words only, without the aid of any further designa- 

 tion, it follows that a generic name should only have one meaning — in other 

 words, that two genera should never bear the same name. For a similar 

 reason, no two species in the same genus should bear the same name. When 

 these cases occur, the later of the two duplicate names should be cancelled, 

 and a new term, or the earliest synonym, if there be any, substituted. 

 When it is necessary to form new words for this purpose, it is desirable to 

 make them bear some analogy to those which they are destined to supersede, 

 as where the genus of birds Plectorhynchus, being preoccupied in Ichthyology, 

 is changed to Plectorhamphus. It is, we conceive, the bounden duty of an 

 author, when naming a new genus, to ascertain by careful search that the 

 name which he proposes to employ has not been previously adopted in other 

 departments of natural history*. By neglecting this precaution he is liable 

 to have the name altered and his authority superseded by the first subsequent 

 aiithor who may detect the oversight, and for this result, however unfortu- 

 nate, we fear there is no remedy, though such cases would be less frequent 



# This laborious and difficult research is now greatly facilitated by the very useful 

 work of M. Agassiz, entitled " Nomenclator Zoologicus," and "Index Universalis " to 

 that work. 



1865. D 



