270 Proposed Reform of Zoological Nomenclature. 
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 
whose characters are now deemed insuficient, 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 together into one. In such cases the law of 
priority forbids us to cancel ali 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 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 excep- 
tions to the law of priority, and in which it becomes both justifi- 
able 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 words 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 cancelled, 
and a new term, or the earliest synonym, if there be any, sub- 
stituted, 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 
