CLASSIFICATION AND DESCRIPTION OF 

 THE COLLECTION. 



What is a Bird ? — A bird may be defined as a feathered 

 vertebrate, or a feathered animal with a backbone. Birds, as we 

 ordinarily see them, look so different from all other animals* that 

 it would seem easy to give a long list of characters, any one of 

 which would serve to distinguish them from mammals, reptiles, 

 and fishes ; yet their only exclusively distinguishing character is 

 their feathers. Birds, it is true, possess horny beaks, and are 

 without teeth, yet some of the early forms of birds had teeth ; and 

 turtles, as well as birds, have a horny beak. Birds lay eggs ; and 

 so do nearly all reptiles and fishes, and some mammals. 



In the ordinary bird there is nothing suggestive of reptilian 

 affinities. Yet birds have not only unquestionably descended from 

 reptilian ancestors, but to-day find their nearest relatives in the 

 scaly, creeping saurian. Birds are so much more nearly related 

 to reptiles than they are to mammals that naturalists now combine 

 them as one of the three grand divisions of Vertebrates, under the 

 name Sauropsida (reptile-like animals), in contrast on the one 

 hand with mammals {^Mammalia), and on the other with frogs, 

 newts, salamanders, and fishes, collectively termed Ichthyopsida 

 (fish-like animals). The connecting links between birds and 

 reptiles, however, are furnished, not by existing forms, but by 

 extinct types of both birds and reptiles, the early types of birds 

 presenting many reptilian features not shown by living birds, 

 while some of the extinct reptiles were more bird-like than any 

 now existing. 



While birds are distinctively characterized by their feathers, 

 they may also be further defined with considerable accuracy as 

 warm-blooded, egg-laying, flying vertebrates. It having been 

 recently discovered, however, that the Duck-billed Platypus and 

 the Echidnas, which are true mammals, lay eggs, this long-current 



