218 
DRAGONS OF THE PRIME. 
Oct., 1891. 
(1) The relation of tlieir structure to their mode of life 
and surroundings, that is, their adaptation to environment. 
(2) The relation of their structure to that of other animals, 
i.e., their position in the pedigree of animals. In this con¬ 
nection some of these old reptiles are of great interest and 
importance, as affording good proof of the evolution of one 
series of animals from another, for they form links in the 
chain of life, and connect together animals which are now 
very different in structure. 
Let us first consider the Ichthyosaurus. This animal lived 
in the seas of the Mesozoic Age, and, as its name indicates, 
is in structure partly like a reptile, partly like a fish ; or, in 
other words, it combines characters some of which are dis¬ 
tinctive of the class of fishes, some of the class of reptiles. It 
is, on the whole, distinctly a reptile, but a lowly organised one. 
In shape Ichthyosaurus was “ very like a whale,” or rather 
a porpoise, for the body was somewhat blunt in front, and 
tapered behind into a long powerful tail,which carried a vertical 
fin. (Fig. 1.) Being of such a shape, the animal was admirably 
adapted for movement in the water. Its skin was, perhaps, 
smooth, and without scales ; if scales were present they were 
not so thick and strong as those with which living reptiles 
are covered, the animal depending for defence from enemies 
on its own powers of offence. 
Attached to the trunk, were four limbs, one pair in front, 
one behind : they had the form of paddles. The Ichthyo¬ 
saurs varied in size. Some were small, others large—the 
largest individuals known are 30ft. long. The head was very 
large in proportion to the body, being a quarter of the whole 
length. It was united to the trunk by a very short neck 
only. The jaws were very long, and were armed with great 
sharp teeth like those of crocodiles. With these jaws the 
fierce Ichthyosaurus seized its prey, and depended for its 
existence on the quickness with which it could move up and 
down in the water, and from side to side in pursuit of the 
animals which formed its food. Since the neck was so short, 
the head could not be moved to any great extent from side to 
side without corresponding movements of the whole body. 
How, then, were they effected ? By means of the vertical tail- 
fin, by the motion of which Ichthyosaurus was able to dart 
from side to side with great ease and swiftness, just as the 
porpoise and grampus do. The motion of the body in other 
directions was produced by the movement of the paddles. 
These organs were quite different from the fins of fishes, and 
somewhat resembled the flappers of whales and porpoises. 
Each paddle or flapper (Fig. 3) was made up of bones which 
