Because the ichthyosaurs were born alive, and because so many of their skeletons are found with their various parts in orderly relation to each other, it is inferred with much probability that they were inhabitants, in large part at least, if not exclusively, of the open and deeper oceans. Had they been oviparous they must necessarily have laid their eggs upon the beaches, since no reptiles of the present time lay eggs in the water, and we have no other indications that the reptiles of the past have ever done so. And such habits would necessitate the periodical return to land. Had they been denizens of shallow waters, like the mosasaurs and plesiosaurs for the most part, their skeletons must surely have been disturbed by the currents and tides, as also by predaceous fishes, breaking up or displacing them or carrying away their bones. In shallow waters, also, the decomposing bodies would have been more liable to despoliation by the many scavengers of the seas. The ichthyosaurs must have been quite helpless upon land, their limbs being of little more use for locomotion than are the fins of fishes. Breathing air as they did, they were of course not suffocated when exposed, unless, as is the case with the whales, the feeble attachment of the ribs prevented the action of the respiratory muscles. If accidentally thrown upon the beaches, they doubtless were able to return to their home element more easily than the fishes can, by flopping, wriggling, and turning. As we have seen, the food consisted in part, perhaps the larger part, of small invertebrates, and because the bones of the lower jaws were closely united, permitting little or none of that expansion so characteristic of the snakes, all their prey must have been of relatively small size. In habit the ichthyosaurs were doubtless, like the dolphins and gavials, inoffensive and harmless, so far as animals of larger size were concerned. The abundance of their remains often found in restricted localities, while deposits of like age and character not far distant may be almost free from them, suggests that in all probability the ichthyosaurs, or the later ones at least, were more or less gregarious in habit as are the sea-mammals. They probably lived in schools, as do the porpoises, each species keeping to its restricted locality and not wandering far.