approaching, they swam away with incredible speed. A flock of them must have resembled the shipping of a harbor with tall masts yellowing in the sunlight. At the base of the long necks were elephantine bodies, and behind, long, tapering tails. Forward and behind were two sets of paddles, perhaps terminating with webbed digits. With the forward paddles Cope thought that they might have seized prey; with all four paddles they swam. From thirty to sixty feet in length, they were well adapted to the deepest waters and to breast the waves of the seas. Like swans and Floridian snake birds, they plunged their necks downward for prey, the body perhaps remaining on the surface as an anchor. Carnivorous, the elasmosaur ate what it could seize, and to-day, with its bones, are found the bones of its victims, usually fishes. Somewhat similar were the cimoliosaurs, even longer necked at times, but with shorter and more powerful tails. Their paddles were long, and as swimmers they must have had few equals in speed. Smooth silicious pebbles to the amount of a peck or two have been found in numerous instances associated with the remains of plesiosaurs of various kinds. They evidently formed a part of the contents of their stomachs, but their use is not clear. But the real rulers of the Cretaceous ocean were the pythonomorphs, or mosasaurs, more like the typical serpents of to-day, and more entitled to be called sea serpents.
The mosasaurs were more elongated and graceful in form. Their heads were large, flat, and conical, with the eyes directed laterally. The tails were long. They had fore and aft paddles with webbed digits, attached to the body with wide peduncles. With paddles and flattened tails they swam with ease and speed. Like snakes, they had four rows of formidable teeth on the roof of the mouth, not for mastication, but for seizing prey and holding it. Like snakes, they swallowed their prey entire, but, unlike snakes, they had not elastic throats. The jaw was, however, so articulated, jointed so far back between the ear and chin, ball-and-socket fashion, that the immense opening made up for the lack of expansibility of throat. The ends of the jaws were bound by flexible ligaments, permitting the passage of large fish or other prey. The mouth of the gullet was prolonged forward while swallowing, evidently being loose and baggy. The same habit pushed forward the glottis, or opening of the windpipe in front of the gullet. Like a serpent, the mosasaur hissed, owing to these formations. The tongue was long and forked, and when at rest was inclosed in a sheath beneath the windpipe and thrown out when the jaws were in motion. And thus, too, are the nearest living forms.
The mosasaurs attained great length, reaching from ten to fifty feet. They had long, projecting muzzles, somewhat like that of the
