68 ANIMALS OF THE PAST 
not know. Did they devour everything large 
enough to be eaten throughout their habitat, 
and then fall to eating one another? Again, 
we do not know. But perish they did, while 
the smaller white shark, which came into being 
at the same time, still lives, as if to emphasize 
the fact that it is best not to overdo things, 
and that in the long run the victory is not 
always to the largest. 
REFERENCES 
The finest Mosasaur skeleton ever discovered, an 
almost complete skeleton of Tylosaurus dyspelor, 29 feet 
in length, may be seen at the head of the staircase lead- 
ing: to the Hall of Paleontology, in the American Museum 
of Natural History, New York. Another good specimen 
may be seen in the Yale University Museum, which prob- 
: ably has the largest collection of Mosasaurs in existence. 
Another fine collection is in the Museum of the State 
University of Kansas, at Lawrence. 
The best Zeuglodon, the first to show the vestigial hind 
legs and to make clear other portions of the structure, is 
m the United States National Museum. 
The great sharks are known in this country by their 
teeth only, and, as these are common in the phosphate 
— 
ie i i 
rns Dee 
