254 AMPHIBIOUS SAURIANS. 
between the period at which they leave the egg 
and then' full maturity, they are provided with 
a more frequent succession of teeth than the 
mammalia, in order to maintain a duly propor- 
tioned supply during every period of their life. 
As the predaceous habits of these animals cause 
their teeth, placed in so long a jaw, to be pe- 
culiarly liable to destruction, the same provision 
serves also to renew the losses which must often 
be occasioned by accidental fracture. 
The existence of these remedial forces, thus 
uniformly adapted to supply anticipated wants, 
and to repair foreseen injuries, affords an ex- 
ample of those supplementary contrivances, 
which give double strength to the argument 
from design, in proof of the agency of Intelli- 
gence, in the construction and renovation of 
the animal machinery in which such contri- 
vances are introduced. 
The discovery of Crocodilean forms so nearly 
allied to the living Gavial, in the same early 
strata that contain the first traces of the Ich- 
thyosaurus and the Plesiosaurus, is a fact which 
seems wholly at variance with every theory that 
would derive the race of Crocodiles from Ichthy- 
osauri and Plesiosauri, by any process of gradual 
transmutation or developement. The first ap- 
pearance of all these three families of reptiles 
seems to have been nearly simultaneous ; and 
they all continued to exist together until the ter- 
