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ON THE CLASSIFICATION OF BIRDS. 



perfection of the class ; just as do the Quadrumana 

 among quadrupeds. 



(17.) III. The order Natatores indicates the po- 

 sition of the swimming tribes ; those whose feet are 

 formed almost exclusively for swimming, and who ha- 

 bitually live in the water. The duck and the goose 

 are familiar examples ; but, to see this structure highly 

 developed, we must turn to the cormorant, the pe- 

 licans, the grebes, and the puffins. The wings, in 

 general, are very short in such as have the feet greatly 

 developed, as in the two last mentioned families : but 

 sometimes we find this preponderance reversed, for in 

 the pelicans the wings are remarkably long and the feet 

 weak. In the gulls and terns, again, both wings and 

 feet are highly organised, so that it might lead us to 

 suspect those birds were the types of the whole order. 



(18.) IV. In the Grallatores, or waders, we have a 

 continuation of aquatic, but not of perfect swimming 

 birds. They are chiefly known by their long legs and 

 half- webbed toes ; a structure which enables them to 

 wade sufficiently deep into the water to capture the ma- 

 rine animals upon which they feed : in this they are 

 greatly assisted by their long, slender, and often flexible 

 bill, which they thrust into the mud and sand, and by 

 this means burrow, like pigs, for worms and other 

 small objects {fig. 4. a). It is clear that their food is 

 sucked up, for the mouth itself is (typically) very 

 small ; and in this respect they perfectly resemble the 



Trochilidce {fig. 4. b), the most suctorial of all birds. 

 In both these groups, the feathers advance very far 

 upon the bill ; and in both we find those birds which 



