﻿142 ON THE CLASSIFICATION OP BIRDS. 



although this part of our subject has expanded itself to 

 wider limits than were originally anticipated. The first 

 of these is seen in the singular and rare genus Orthonyx, 

 one of the very few scansorial birds of Australia, and 

 which seems to partake of the anomalous, or rather 

 unusual structure so prevalent among the animals of 

 that region. It will be necessary, however, before we 

 can understand how a bird like Orthonyx, — whose great 

 and long foot resembles that of the rasorial order, — can be 

 connected with Dendrocolaptes, that we look to the genus 

 Sclerurus (fig* 7 6.), an equally rare type, from the forests 



of Brazil, and of 

 which the only 

 specimen we 

 have yet seen is 

 in our museum. 

 The foot of this 

 bird has much of 

 the general cha- 

 racter of Dendro- 

 colaptes, but the 



tarsus is much longer, and the outer toe (a), instead of 

 being equal to the middle one (b), is shorter ; the claws 

 are also smaller, weaker, and less curved : in all this dimi- 

 nution of the scansorial powers in these parts, we see a 

 considerable falling off from the typical perfection, and 

 adverting to what we have just advanced on the use of 

 the anterior feet, it is obvious this bird cannot ascend a 

 tree so rapid as a Dendrocolaptes. The same dimi- 

 nution of strength can be traced in the tail, the shafts 

 of which, although rigid, are comparatively weaker, 

 and do not extend beyond the webs, as in all the rest of 

 the CerthiancB. Yet still, as this bird belongs to the 

 pre-eminent group of the tree creepers, its powers 

 should not be so very much diminished ; and we con- 

 sequently find that the comparative weakness of its 

 other members is made up by a great elongation of the 

 hinder toe (c), which is one half as long again as in Den- 

 drocolaptes (fig. 75.)j> so that it becomes, as in the nut- 



