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ON THE CLASSIFICATION OF BIRDS. 



probable that the three last — which constitute the aber- 

 rant group of the class — are only of the rank of tribes ; 

 equivalent to the Fissirostres, Scansores, &c. hereafter 

 noticed. As the circularity of these three groups, taken 

 collectively, has not yet been made out, we shall there- 

 fore, for the present, consider them as holding the rank 

 of orders. The typical circle is seen in the order Inses- 

 sores, and the subtypical in that of the Raptores. 

 Groups, truly natural, may be denned by more than 

 one set of characters ; hence it is, that, independent of 

 every other, the primary divisions of this class may be 

 shortly and beautifully discriminated by their feet. In 

 these members we have three striking modifications of 

 structure (fig. 2.). In the Raptores, or birds of prey 



the feet (a) are raptorial ; that is, adapted for seizing and 

 destroying other animals ; the claws are consequently 

 sharp, much hooked, and retractile, and they may be em- 

 ployed both offensively and defensively. In the second, 

 or pre-eminent type — the Insessores — the feet are 

 constructed more especially for grasping or perching (b) ; 

 the claws are comparatively small, less curved, and are 

 not retractile ; while the hind toe, as in the last, is 

 placed upon the same level as the fore toes. In the third, 

 or aberrant division, composed of the fowls (c), the 

 waders (d), and the swimmers (e), none of the above 

 characters are found. The hind toe, when it exists, is 

 always elevated above the plane of the others, and the fore 

 toes are more or less connected by a membrane. The 



