CHAPTER XVII 
THE BIRDS 
189. Characteristics—Birds form one of the most sharp- 
ly defined classes in the animal kingdom, and the variations 
among the different species are relatively small. “The 
ostrich or emu and the raven, for example, which may be 
said to stand at opposite ends of the series, present no such 
anatomical differences as may be found between a common 
lizard and a chameleon, or between a turtle and a tortoise,” 
and these we know to be relatively slight. 
In many respects the birds resemble the reptiles, and 
long ago in the world’s history the relationship was much 
closer than now, as we know from certain fossil remains in 
this country and in Europe. One‘of the earliest of these 
fossil birds, that of the Archeopteryx, is a most remarkable 
combination of bird and lizard. Unlike any modern bird, 
the jaws were provided with many conical reptile-like teeth. 
The wings were rather small, and the fingers, tipped with 
claws, were distinct, not grown together, as in modern birds. 
The tail was as long as the body, and many-jointed, like a 
lizard’s, each vertebra carrying two long feathers. The 
bird was about the size of a crow, and it probably could 
not fly far. Other ancient types have been discovered— 
principally sea-birds—many of which existed when the 
Pacific extended over the region now occupied by the 
Rocky Mountains. These were all of the same generalized 
type, intermediate between reptile and bird. This fact 
leads us to the belief that birds descended from reptilian 
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