Of all these strange old forms, so singularly uniting features of Fishes and Reptiles, none has given rise to more discussion than the Pterodactylus, (Figure 3,) another of the Saurian tribe, associated, however, with Birds by some naturalists, on account of its large wing-like appendages. From the extraordinary length of its anterior limbs, they have generally been described as wings, and the animal is usually represented as a flying Reptile. But if we consider its whole structure, this does not seem probable, and I believe it to have been an essentially aquatic animal, moving after the fashion of the Sea-Turtle. Its so-called wings resemble in structure the front paddles of the Sea-Turtles far more than the wings of a Bird; differing from them, indeed, only by the extraordinary length of the inner toe, while the outer ones are comparatively much shorter. But, notwithstanding this difference, the hand of the Pterodactylus is constructed like that of an aquatic swimming marine Reptile; and I believe, that, if we represent it with its long neck stretched upon the water, its large head furnished with powerful, well-armed jaws, ready to dive after the innumerable smaller animals living in the same ocean, we shall have a more natural picture of its habits than if we consider it as a flying animal, which it is generally supposed to have been. It has not the powerful breast-bone, with the large projecting keel along the middle line, such as exists in all the flying animals. Its breast-bone, on the contrary, is thin and flat, like that of the present Sea-Turtle; and if it moved through the water by the help of its long flappers, as the Sea-Turtle does now, it could well dispense with that powerful construction of the breast-bone so essential to all animals which fly through the air. Again, the powerful teeth, long and conical, placed at considerable intervals in the jaw, constitute a feature common to all predaceous aquatic animals, and would seem to have been utterly useless in a flying animal at that time, since there were no aerial beings of any size to prey upon. The Dragon-Flies found in the same deposits with the Pterodactylus were certainly not a game requiring so powerful a battery of attack.