2i8 POPULAR SCIENCE MONTHLY. 



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 with- 

 out the aid of limbs, and these were not at all fitted for land locomo- 

 tion. 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 Por- 

 theus 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, sink- 

 ing 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 propor- 

 tions, and which may have been both pursued and pursuer, accord- 

 ing to size of mosasaur and pterosaur. The pterosaur had a wing- 

 expanse of eighteen to nineteen feet, as instanced in Ornitliostoma 

 umbrosum (Cope), the largest in size, and 0. 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 them- 

 selves 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 Creta- 

 ceous seas. The Protostega gigas (Cope), figured herein from a 

 drawing by Prof. E. C. Case,* of Wisconsin, was the largest, its flip- 

 pers 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 incom- 

 plete as to leave the matter in doubt, it is interesting to note Professor 

 Williston's discoveries of quite perfect fore and aft paddles of mosa- 



* Professor Case, the authority on this marine turtle, says : The skin must have been 

 smooth and leathery, with supporting ridges or folds of dorsal integument to strengthen 

 the back, perhaps two or three on either side of the central ridge. The back must have 

 been quite flat. There were no claws on the front foot. The skull was as represented in 

 the drawing. 



