Observations on some Species of Motacilla. 459 



systems. From the naked prehensile-tailed Opossums of 

 South America, for instance, we have a gradual and uninter- 

 rupted transition, through the equally naked-tailed Coescoes 

 (Balantia) of the Indian Isles, to the true Phalangers ; and 

 from these to the Petaurists directly on the one hand, and, by 

 means of the Pseudocheirs, to the Koalas on the other. Here 

 the chain is perfectly unbroken, and the affinities of the dif- 

 ferent genera too obvious to be overlooked ; and this new re- 

 lation, added to their common habits, appetites, and economy, 

 the conformity of structure displayed in their organs of sense 

 and prehension, and the marsupial character of the whole 

 tribe, constitutes a mass of evidence in favour of the approxi- 

 mation of these animals which I have here made, as strong as 

 that which supports almost any other natural family. I pro- 

 pose, therefore, to distinguish the present group by the name 

 of Didelphidas, in allusion at once to its most remarkable cha- 

 racter, and to the principal genus of which it is composed, 

 ( To be continued.*) 



Art. II. Observations on some Species of the Genus Motacilla of 

 Linnaeus. By John Gould, Esq., F.L.S., &c. 



Having recently brought before the notice of the Zoologi- 

 cal Society? at one of the scientific meetings, a few remarkable 

 facts respecting the limited range of some of our native birds, 

 and the strictness with which they are confined to certain 

 localities, I hastily transmit a few additional observations, 

 which, as they principally relate to one of the most elegant 

 and familiar of the British birds, may, perhaps, be worthy of 

 a place in the Magazine of Natural History, where they will 

 meet the eyes of many devoted exclusively to the study of 

 British ornithology, and, perhaps, induce a more minute in- 

 vestigation of the subject to which the present observations 

 are directed. 



The distinctions pointed out by me, a few years since, 

 between the yellow wagtail of the British islands (Motacilla 

 flava Ray) and the species commonly seen on the neighbouring 

 continent, which I have named M. neglecta, are now, I believe, 

 well known to most of your readers. My views respecting 

 the separation of these species have since been confirmed by 

 the opinions of ornithologists generally ; and, although a few 

 solitary specimens have been discovered in Britain, it must be 

 admitted that the shores of France and Holland constitute 

 the western boundary of the species ; while, as far as my 

 observations go, the British islands constitute as exclusively 



