Birds

Excerpt from The Elements of Ornithology

All Birds have feathers, and no such thing as a feather is possessed by any creature which is not a Bird. This character alone, therefore, suffices to define the whole Class. The uniformity of their structure is very remarkable. While some beasts, some reptiles, and some fishes have but a pair of limbs, and other reptiles and fishes have none, all Birds have two pairs  a pair of wings and apair of legs. Most beasts and reptiles have a long tail, while some are without any; but every existing Bird has a tail which, feathers apart, is short T. Some beasts, some reptiles, and some fishes are edentulous, while most have teeth; but no living Bird possesses such structures. Some beasts, some reptiles, and some fishes are eyeless but every Bird has a pair of eyes. Birds are eminently aerial creatures, and there are but very few which have no power of ?ight; while none of the living members of the other Classes can truly ?y except Bats; though some ancient reptiles (pterodactyles) possessed a similar power. Although many birds are more or less aquatic in their habits, none are so completely so as either the Whales and Porpoises amongst beasts, or certain reptiles.