But the wonders of Mesozoic reptiles are not yet exhausted. While noticing numerous crocodiles and lizard: like creatures, and several kinds of tortoises, we are startled by what seems a flight of great bats, wheeling and screaming overhead, pouncing on smaller creatures of their own kind, as hawks seize sparrows and partridges, and perhaps diving into the sea for fish. These were the Pterodactyles, the reptile bats of the Mesozoic. They fly by means of a membrane stretched on a monstrously enlarged little finger, while the other fingers of the fore limb are left free to be used as hands or feet. To move these wings, they had large breast-muscles like those of birds. In their general structure, they were lizards, but no doubt of far higher organization then any animals of this order now living; and in accordance with this, the interior of their skull shows that they must have had a brain comparable with that of birds, which, they rivalled in energy and intelligence. Some of them were larger then the largest modern birds of prey, others were like pigeons and snipes in size. Specimens in the Cambridge Museum indicate one species twenty feet in the expanse of its wings. Cope has recently described an equally gigantic species from the Mesozoic of Western America, and fragments of much larger species are said to exist.[AE] Imagine such a creature, a flying dragon, with vast skinny wings, its body, perhaps, covered with scales, both wings and feet armed with strong claws, and with long jaws furnished with sharp teeth. Nothing can be conceived more strange and frightful. Some of them had the hind limbs long, like wading birds. Some had short, legs, adapted perhaps for perching. They could probably fold up their wings, and walk on all fours. Their skeleton, like that of birds, was very light, yet strong; and the hollow bones have pores, which show that, as in birds, air could be introduced into them from the lungs. This proves a circulation resembling that of birds, and warm blood. Indeed, in many respects, these creatures bridge over the space between the birds and the reptiles. "That they lived," says Seeley, "exclusively upon land or in the air is improbable, considering the circumstances under which their remains are found. It is likely that they haunted the sea-shores; and while sometimes rowing themselves over the water with their powerful wings, used the wing membrane, as does the bat, to encloses the prey and bring it to the mouth. The large Pterodactyles probably pursued a more substantial prey then dragon-flies. Their teeth were well suited for fish; but probably fowl and small mammal, and even fruits, made a variety in their food. As the lord of the cliff, it may be supposed to have taken toll of all animals that could be conquered with tooth and nail. From its brain, it might be regarded as an intelligent animal. The jaws present indications of having been sheathed with a horny