Apr. 1903. NorTH AMERICAN PLESIOSAURS—WILLISTON. ug 
‘ 
hypothesis that they were swallowed by the animal with food, as is 
the case with several living reptiles and birds. If this view should be 
held admissible, it would suggest that, as the teeth were too small 
for anything but prehension, a structure analogous to a gizzard or the 
stomach of an edentate, may have used these pebbles to assist in 
breaking up or crushing the food.on which the saurian lived.” 
