54 ANIMALS OF THE PAST 
is a sort of joint in each half of the lower jaw 
which permits it to bow outward when opened, 
and this, aided by the articulation of the jaw 
with the cranium, adds greatly to the swallow- 
ing capacity. Thus in nature the same end is 
attained by very different methods. ‘To bor: 
row a suggestion from Professor Cope, if the 
reader will extend his arms at full length, the 
palms touching, and then bend his elbows out- 
ward he will get a very good idea of the ac- 
Fig. 10. — Jaw of a Mosasaur, Showing the Joint that 
Increased the Swallowing Capacity of that Reptile. 
tion of a Mosasaur’s jaw. The western sea 
was a lively place in the day of the great 
Mosasaurs, for with them swam the king of 
turtles, Archelon, as Mr. Wieland has fitly 
named him, a creature a dozen feet or more in 
length, with a head a full yard long, while in 
the shallows prowled great fishes with massive 
jaws and teeth like spikes. h 
There, too, was the great, toothed diver, 
