306 ZOOLOGICAL NOMENCLATURE. 



[A genus compounded of two or more previously proposed 

 genera whose characters are now deemed insufficient, should retain 

 the name of one them.] 



It sometimes happens that the progress of science requires 

 two or more genera, founded on insufficient or erroneous cha- 

 racters, to be combined together 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 there- 

 tore 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 unobjectionable, 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 considered sufficiently distinct in character, are now united 

 under the general name of Accentor, that being the earliest. 

 So also Cerithium and Potamides, which were long considered 

 distinct, are now united, and the latter name merges into 

 the former. 



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 when previously applied to another 

 group which still retains it.~\ 



It being essential to the binomial method to indicate objects 

 in natural history by means of two icords only, without the 

 aid of any further designation, 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 caucelled, and a new term, or the earliest sjmonym, 

 if there be any, substituted. Wheu 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 

 whei'e the genus of birds P lector hynchus, being pre-occupied in 

 Ichthyology, is changed to Plectorhamphus. It is, we conceive, 

 the bouuden duty of an author, when naming a new genus, 

 to ascertain by careful search that the name which he proposes 



