212 University of Kansas Geological Survey. 



a length of thirty-seven or thirty-eight feet, and some species 

 yet larger are, I believe, reported from Europe. I am confident, 

 however, that there never has been a Mosasaur in existence — 

 certainly none whose remains are now known — whose length 

 was greater that forty-five feet. The text-books and popular, 

 descriptions place the length of these animals at from 75 to 100 

 feet. 



The habits of the animals when alive are not hard to conjec- 

 ture. They were marine lizards, living for the most part in 

 shallow waters, though, often, especially the largest species, 

 venturing far out to sea. That they did not usually frequent 

 deep water, as did the Plesiosaurs, is probable. There are peb- 

 bles from the stomach of a Plesiosaur in the University museum 

 which must have been brought to Kansas from hundreds of 

 miles away — longer journeys than I believe the Mosasaurs ever 

 made. Perhaps this fact will account for the entire absence, so 

 far, of the Mosasaurs in the Benton rocks, while they do occur 

 most abundantly in the shallower water deposits of the Niobrara 

 in Kansas, especially towards the close of the epoch. 



While the flexibility and loose union of the jaws doubtless 

 permitted animals of considerable size to be swallowed, the 

 structure of the pectoral girdle would never have permitted any 

 such feats of deglutition of which the python and boa are 

 capable. It has-been supposed that the lower jaws were capa- 

 ble of an anterior prolongation in swallowing their prey, but 

 such must have been very slight, since the union with the 

 pterygoid is too firm to permit much, if any, motion here. In 

 the pictures of the skull, the remarkable, though incomplete, 

 ball-and-socket joint back of the middle of the jaw is conspicu- 

 ous, differing in this respect from all other reptiles, ancient 

 or modern. That there was any degree of vertical motion 

 here is scarcely possible, since the union of the jaw above was 

 too close. As has been described, a thin plate of bone passed 

 across the joint and was ensheathed within the presplenial, per- 

 mitting probably a small amount of lateral bending, but little 

 or none of vertical. The animals living in the water, with no 

 solid objects to aid in deglutition, the body not serpentine 



