Mr. A. R. Wallace on the Natural Arrangement of Birds. 211 



modification of the normal (f-toed) foot which is adapted for 

 climbing. In the Woodpeckers,, however, we find the outer toe 

 always turned completely backwards, and therefore quite free 

 from the middle toe. The true hind toe is also invariably small 

 and weak, and of so little importance that in several species of 

 Woodpeckers it is altogether wanting, without at all diminishing 

 the bird^s powers of climbing. If we compare this foot with 

 that of the other Scansores, we shall find that it is an extreme 

 modification of the Scansorial form, adapted for true climbing. 

 The toes are all more powerful, the claws much stronger, the 

 outer toe longer, and the hind toe smaller. If therefore the 

 structure of foot in the Cuckoos and Turacos, where the outer 

 toe can be placed either forward or backward and the hind toe 

 remains moderately developed, is (as is universally allowed) the 

 link between the f-toed and y-toed form, then it follows that of 

 all f-toedfeet the Woodpecker's is most removed from the f-toed, 

 and of all f -toed feet the Creeper's is the furthest removed from 

 the -|-toed; — and thence as a further deduction it follows, that 

 the feet of the Creepers and Woodpeckers are the furthest pos- 

 sible removed from each other. When, in addition to this re- 

 markable result, we consider that the structure of the climbing 

 tail is totally dissimilar in the two cases, we shall see that there 

 exist no grounds whatever for establishing an afiinity between 

 the two families, and that the Creepers must not only be sepa- 

 rated from the Scansores, but in a natural arrangement will be 

 placed at a very considerable distance from them. 



The Musophagidce, containing the Turacos and Plantain- 

 eaters, have been placed among the Scansores by the conti- 

 nental ornithologists (Temminck and Vieillot), while in England 

 they have been considered to be Conirostres by Swainson and 

 Gray. We believe the former are correct ; for these birds have 

 the short, rounded and weak wings of the Cuckoos and Toucans, 

 and consequently very imperfect flight, while their legs are very 

 strong, the outer toe long and versatile, but rather less so than 

 in the Cuckoos, and the hind toe, as in all Scansores, short. 

 Their habits are described as being almost exactly those of the 

 Toucans and Barbets, their plumage is of a similar texture, while 

 the short crest at the back of the head is similar^ to that of the 

 Woodpeckers. Some species are said to be able to cling to ver- 

 tical trunks. Their internal structure and the form of the ster- 

 num appear to correspond exactly to this view of their affinities, 

 which is still further confirmed by their nidification, like that of 

 all other Scansores, in hollow trees, so that they may be well 

 placed in the wide interval between the Cuckoos and Toucans 



14* 



