When we come to discuss the topic of the earliest bird--not the one in the proverb--our choice of subjects is indeed limited, being restricted to the famous and oft-described Archaeopteryx from the quarries of Solenhofen, which at present forms the starting-point in the history of the feathered race. Bird-like, or at least feathered, creatures, must have existed before this, as it is improbable that feathers and flight were acquired at one bound, and this lends probability to the view that at least some of the tracks in the Connecticut Valley are really the footprints of birds. Not birds as we now know them, but still creatures wearing feathers, these being the distinctive badge and livery of the order. For we may well speak of the feathered race, the exclusive prerogative of the bird being not flight but feathers; no bird is without them, no other creature wears them, so that birds may be exactly defined in two words, feathered animals. Reptiles, and even mammals, may go quite naked or cover themselves with a defensive armor of bony plates or horny scales; but under the blaze of the tropical sun or in the chill waters of arctic seas birds wear feathers only, although in the penguins the feathers have become so changed that their identity is almost lost. [Illustration: Fig. 13.--Archaeopteryx, the Earliest Known Bird. _From the specimen in the Berlin Museum._] So far as flight goes, there is one entire order of mammals, whose members, the bats, are quite as much at home in the air as the birds themselves, and in bygone days the empire of the air belonged to the pterodactyls; even frogs and fishes have tried to fly, and some of the latter have nearly succeeded in the attempt. As for wings, it may be said that they are made on very different patterns in such animals as the pterodactyl, bat, and bird, and that while the end to be achieved is the same, it is reached by very different methods. The wing membrane of a bat is spread between his out-stretched fingers, the thumb alone being left free, while in the pterodactyl the thumb is wanting and the membrane supported only by what in us is the little finger, a term that is a decided misnomer in the case of the pterodactyl. In birds the fingers have lost their individuality, and are modified for the attachment or support of the wing feathers, but in Archaeopteryx the hand had not reached this stage, for the fingers were partly free and tipped with claws. [Illustration: Fig. 14.--Nature's Four Methods of Making a Wing. Bat, Pterodactyl, Archaeopteryx, and Modern Bird.]