The Crocodilians also appear in the later Triassic, abound in the Jurassic, and give way before the later types, the true Crocodiles, in the Cretaceous. They were marine animals with naked skin, a head and neck something like that of the Ichthyosaur, and paddles like those of the Plesiosaur. Their back limbs, however, were not much changed after their adaptation to life in the sea, and it is concluded that they visited the land to lay their eggs. The Teleosaur was a formidable narrow-spouted reptile, somewhat resembling the crocodiles of the Ganges in the external form of the jaws. The modern crocodiles, which replaced this ancient race of sea-crocodiles, have a great advantage over them in the fact that their nostrils open into the mouth in its lower depths. They can therefore close their teeth on their prey under water and breathe through the nose. Snakes are not found until the close of the Mesozoic, and do not figure in its characteristic reptile population. We will consider them later. But there was a large group of reptiles in the later Mesozoic seas which more or less correspond to the legendary idea of a sea-serpent. These Dolichosaurs ("long reptiles") appear at the beginning of the Chalk period, and develop into a group, the Mososaurians, which must have added considerably to the terrors of the shore-waters. Their slender scale-covered bodies were commonly twenty to thirty feet in length. The supreme representative of the order, the Mososaur, of which about forty species are known, was sometimes seventy-five feet long. It had two pairs of paddles--so that the name of sea-serpent is very imperfectly applicable--and four rows of formidable teeth on the roof of its mouth. Like the Deinosaurs and Pterosaurs, the order was doomed to be entirely extinguished after a brief supremacy in its environment.