me DISTRIBUTION OF BIRDS. 
in minor points, is still near enough to the truth to give 
a correct idea of this extraordinary bird’s appearance. 
The Archzopteryx was about the size of a Crow. Its 
long, feathered tail is supposed to have acted as an aéro- 
plane, assisting in the support of the bird while it was 
in the air, but its power of flight was doubtless limited. 
It was arboreal and probably never descended to the 
earth, but climbed about the branches of trees, using its 
large, hooked fingers in passing from limb to limb. 
The wanderings of this almost quadrupedal creature 
must necessarily have been limited, but its winged de- 
scendants of to-day are more generally distributed than 
are any other animals.* They roam the earth from pole 
to pole; they are equally at home on a wave-washed 
coral reef or in an arid desert, amid arctic snows or in 
the shades of a tropical forest. This is due not alone to 
their powers of flight but to their adaptability to vary- 
ing conditions of life. Although, as I have said, birds 
are more closely related among themselves than are the 
members of either of the other higher groups of animals, 
and all birds agree in possessing the more important 
distinguishing chiracters of their class, yet they show a 
wide range of variation in structure. 
This, in most instances, is closely related to habits, 
* On the distribution of animals read Allen, The Geographical 
Distribution of North American Mammals, Bulletin of the American 
Museum of Natural History, New York city, iv, 1892, pp. 199-244; 
four maps. Allen, The Geographical Origin and Distribution of North 
American Birds considered in Relation to Faunal Areas of North 
America, The Auk (New York city), x. 1893, pp. 97-150; two maps, 
Merriam, The Geographic Distribution of Life in North’ America, with 
Special Reference to Mammalia, Proceedings of the Biological Society 
of Washington, vii, 1892, pp. 1-64; one map. Merriam, Laws of Tem- 
emgedigteey of the Geographic Distribution of Terrestrial Ani- 
mals and Plants, National Geographic Magazine (Washington 
1894, pp. 229-238; three maps, Bra pias 
