PLESIOSAURUS. 211 
series of links and gradations, from the corres- 
ponding parts of the highest mammalia, to their 
least perfect form in the fins of fishes. In the 
fore paddle of the Plesiosaurus, we have all the 
essential parts of the fore leg of a quadruped, 
and even of a human arm ; first the scapula, 
next the humerus, then the radius and ulna, 
succeeded by the bones of the carpus and meta- 
carpus, and these followed by five fingers, each 
composed of a continuous series of phalanges. 
(see PI. 16, 17, 19.) The hind paddle also offers 
precisely the same analogies to the leg and foot 
of the Mammalia ; the pelvis and femur are 
succeeded by a tibia and fibula, which articulate 
with the bones of the tarsus and metatarsus, 
followed by the numerous phalanges of five long 
toes. 
From the consideration of all its characters, 
Mr. Conybeare has drawn the following infe- 
rences with respect to the habits of the Plesio- 
saurus Dolichodeirus, " That it was aquatic is 
evident, from the form of its paddles ; that it 
was marine is almost equally so, from the re- 
mains with which it is universally associated ; 
still more numerous and angular joints of the paddle of the 
Ichthyosaurus, and the phalanges of land quadrupeds, which are 
more or less cylindrical ; in these sea Lizards they were flattened, 
for the purpose of giving breadth to the extremities as organs of 
swimming. As its paddles give no indication of having carried 
even such imperfect claws, as those of the Turtles and Seals, 
the Plesiosaurus apparently could have made little or no progress 
in any other element than water. 
