Page:Popular Science Monthly Volume 53.djvu/232

218 of the jaws undoubtedly permitted animals of considerable size to be swallowed, the structure of the thoracic girdle would not have permitted any such feats of deglutition of which the python and boa are capable. The animals must have been practically helpless on land. They were not sufficiently serpentine to move about without the aid of limbs, and these were not at all fitted for land locomotion. They lived in open seas, often remote from the shores. Their pugnacity is amply indicated by the many scars and injuries they received, probably from others of their own kind."

Among the fishes which were the prey of mosasaurs was Portheus molossus (Cope), the most formidable, and whose bulldog teeth and looks indicate that it leveled matters of justice by capturing smaller mosasaurs at times. The head of molossus was twice as large as that of a grizzly bear, the jaws deeper in proportion to length. The muzzle was stouter and deeper than a bulldog's. The teeth had sharp, cylindric fangs, smooth and glistening and of irregular size. Occasionally the teeth projected three inches above the gums, sinking one inch into the pits, as long as the fangs of a tiger and more slender. Two pairs of these long fangs crossed each other on each side of the snout.

Over the water were the flying saurians of formidable proportions, and which may have been both pursued and pursuer, according to size of mosasaur and pterosaur. The pterosaur had a wing expanse of eighteen to nineteen feet, as instanced in Ornithostoma umbrosum (Cope), the largest in size, and O. ingens (Marsh). The pterosaurs flew with leathery wings over the waves, plunging to seize unwary fishes or perhaps to be seized by mosasaurs, or soaring at a safe distance while watching the combats of swimming saurians. At nightfall they trooped along the shores, at last to suspend themselves to the cliffs by the claws of their wing limbs.

If tortoises were food for mosasaurs, there were plenty of marine turtles to choose from. The turtle was the boatman of the Cretaceous seas. The Protostega gigas (Cope), figured herein from a drawing by Prof. E. C. Case, of Wisconsin, was the largest, its flippers having a spread of fifteen feet. Wieland has recently described an immense species, Protostega ischyros, from Wyoming.

Inasmuch as the earlier skeletons of mosasaurs were so incomplete as to leave the matter in doubt, it is interesting to note Professor Williston's discoveries of quite perfect fore and aft paddles of