﻿EXTERNAL ANATOMY. SCANSORIAL FEET. 133 



ordinary perchers, but the tarsus is very short, that is, 

 not longer than the hinder toe : the lateral toes are 

 either equal or not, but the middle one is much shorter 

 than in the jays and other birds, which are both ar- 

 boreal and terrestrial. Another peculiarity of the pre- 

 hensile foot is seen in the claws, which are short, broad, 

 and unusually curved ; by this we know that they are 

 well adapted for enabling the bird to take a firm hold 

 of branches, while they are totally unfitted for terres- 

 trial habits. The common oriole (Oriolus galbula) 

 I sf | will serve to explain this 



\ y\ i > m nlv 69 structure in the absence of 



The foot of the Ampelis garrulus (b) unites this and the 

 insessorial structure, the middle toe being much more 

 lengthened than in any of the last mentioned genera. 



(121.) The last form leads us to those of the Scan- 

 sorial structure, as developed in such birds as have three 

 anterior toes, and one posterior. Of such feet as are 

 especially adapted for climbing, where the toes are dis- 

 posed in pairs, we have already spoken, but there are 

 a great variety of birds possessing the same faculty, 

 and yet exercising it by means of feet very differently 

 constructed. We shall now trace, in the gradual deve- 

 lopment of this structure, all its variations among birds 

 whose toes have the ordinary direction so characteristic 

 in the typical perchers. The sort of foot last defined, 

 and which we have called prehensile, may be con- 

 sidered the first incipient development of the scansorial 

 structure ; the primary distinctions of which is in an 

 unusual elongation of the hinder toe, and a great 

 breadth and curvature of the claws. The short-legged 



any other native bird; but it 

 is much more perfectly deve- 

 loped in the family of short- 

 legged thrushes, including 

 the genera Chloropsis (Jig. 

 6*9- a), Brachypus, Tricho- 

 phoruSy &c, all of which are 

 natives of Africa and India. 



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