EXTINCT MONSTERS 
78 
be considered here. The species shown in Fig. 14 had rather a 
large head. It is obvious that such a long slender neck as these )i 
creatures had could not have supported a large head, like that j 
of the fish-lizard. Consequently, we find a striking contrast in i 
the skulls of the two forms. That of the Plesiosaur was short 11 J 
Fig. 13. — Mandibles of Sea-lizards, a, Peloneustes philarchus (Seeley) ; from 
the Oxford Clay, b, Thaumatosaurus indicus (Lydekker) ; Upper Jurassic of India, 
c, Plesiosaurus dolichodirus (Conybeare) ; from the Lower Lias, Lyme Begis. 
and stout, and therefore such as could easily be supported, as 
well as rapidly moved about by the long slender neck. Thus 
we find another simple illustration of the “ law of correlation,” 
alluded to on p. 7. The teeth were set in distinct sockets, as 
they are in crocodiles, to which animals there are also points 
