Bibliographical Notices. 451 



the known species of birds cannot be calculated to exceed 8000, it 

 seems that we have already split up the genera to such an extent 

 that they contain on the average only about three species apiece. 

 And as it is requisite that iu any natural system the genera should 

 have as nearly as possible the same amount of difference infer se, and 

 these new genera have been created much more abundantly in some 

 groups than in others, it follows that, in order to reduce all the ge- 

 neric divisions to a uniform standard, a vast number of further genera 

 must be created, and we shall ultimately have not more than two or 

 perhaps one species in each genus. 



Such a result would, we suppose, be condemned by every naturalist, 

 but it cannot be avoided if the present system is much longer pur- 

 sued. The fact is that a large proportion of the recently established 

 so-called genera ai'e founded upon such shght differences, that it 

 would be quite impossible to draw up generic characters for them. 

 These modern genus-makers do not hesitate to coin a new appellation 

 for any two or three allied species that resemble each other in colour- 

 ing and form what may be called a homochroous group, without re- 

 flecting that each of the other numerous isolated idiochroous species 

 of the genus have equal claims to similar distinctive separation*. 



But though it cannot be denied that style of colouring is often an 

 excellent guide to affinities, we maintain that generic names are only 

 to be employed where there are real differences in structure, and not 

 where merely the plumage is dissimilar. The appellations applied to 

 these minor groups should be either altogether unnoticed, or merely 

 placed in any arrangement of the species at the head of each group, 

 in the manner shown by Mr. G. R. Gray in the more lately pub- 

 lished Catalogues of the British Museum. 



Even more lamentable than the rapid increase of these generic 

 subdivisions is the fact that many of them have received three or four 

 and even more synonymous appellations from different authors, and 

 some of them more than one from the same author ! In spite of the 

 ' stern law of priority ' now professed to be submitted to by the 

 whole scientific world, several individual writers seem to think little 

 of changing names that they have themselves imposed. Thus we 

 find Strophiolcemvs (18.53) and lolcema (1854) proposed by the same 

 author for the same genus of T/'oc^^Y/r/te, Galbalcijrhijnchus {I'SAo) 

 and Jacarnaralcyonides (1849) for the same genus of Galbulidce, 

 Cyaaopolius (1849) and Cyanopica (1850) for the same genus of 

 Corvldce, and Chlorochrysa and CallipanBa in the same year for the 

 same genus of Tanagers, A^-ithout any apparent excuse for the crea- 

 tion of the second names, unless it be forgetfulness that the first-given 

 had ever been proposed. It is to be hoped that Mr. Gray's Catalogue, 



* In resolving many natural genera into species, it will be found that 

 groups of threes or foui's often show gi-eat similarity in plumage, and are 

 what may be called ' horaochroous' (o^oxpoos, similem colorem hubens). 

 These are generally distributed over different geographical areas, and re- 

 present each other in their respective localities. Other inchvidual species 

 have peculiar colouring of their own, and may be termed idiochroous (iStoy, 

 peculiaris, et XP'^°''^ color). 



30* 



