280 HISTORICAL PALZONTOLOGY. 
trunk greatly shortened; whilst the digits were enclosed in the 
integuments, and constituted paddles, closely resembling in 
structure the “ flippers” of Whales and Dolphins. The neck 
is sometimes moderately long, but oftener very short, as the 
great size and weight of the head would. have led one to anti- 
cipate. Bony plates seem in some species to have formed an 
at any rate partial covering to the skin; but it is not certain 
that these integumentary appendages were present in all. Up- 
on the whole, there can be no doubt but that the Mosasauroid 
Reptiles—the true ‘‘Sea-serpents ” of the Cretaceous period — 
were essentially aquatic in their habits, frequenting the sea, 
and only occasionally coming to the land. 
The ‘‘ Mosasauroids” have generally been regarded as a 
greatly modified group of the Lizards (Lacertilia). Whether 
this reference be correct or not—and recent investigations 
render it dubious—the Cretaceous rocks have yielded the 
remains of small Lizards not widely removed from existing 
forms. ‘The recent order of the Chelonzans is also represented 
in the Cretaceous rocks, 
by forms closely re- 
sembling living types. 
Thus the fresh - water 
deposits of the Wealden 
have yielded examples 
of the “‘Terrapins” or 
‘‘Mud-Turtles” (mys); 
and the marine Creta- 
ceous strata have been 
found to contain the 
remains of various spe- 
cies of Turtles, one of 
which is here figured 
(fig. .2212). . No’ tome 
Serpents ( Ophidia) have 
as yet been detected in 
the Cretaceous rocks; 
and this order does not 
appear to have come 
into existence till the 
Tertiary period. Last- 
ly, true Crocodiles are 
Fig. 211.——Carapace of Chelone Benstedi. Z 
Lower Chalk. (After Owen.) known to have existed 
in considerable num- 
bers in the Cretaceous period. The oldest of these occur 
in the fresh-water deposit of the Wealden; and they differ from 
