222 
DRAGONS OF THE PRIME. 
Oct., 1891 . 
of these likenesses it has been classed with Ichthyosaurus, but 
really it is a very different animal and belongs to a very 
different division of reptiles. The first and most obvious 
difference between the two animals which strikes us is that, 
while Ichthyosaurus had the shortest of necks, Plesiosaurus 
had the longest ; the neck being almost as long as the body 
and tail together, and was, in fact, T 5 F of the whole length. 
Then, again, while the tail was long and powerful in 
Ichthyosaurus, in Plesiosaurus it was short and weak, but 
correlated with this deficiency was the size of the paddles, 
which were much larger proportionally, and much more 
powerful in the latter than in the former. 
Plesiosaurus was well adapted to its environment, but not 
in quite the same way as Ichthyosaurus ; the latter was 
capable of making swift movements ; the former was not so 
swift a swimmer, not possessing a long, powerful tail. Its long 
neck, too, no doubt impeded its progress through the water, 
but at the same time, owing to its length and flexibility, 
Plesiosaurus could dart its head this way and that, in all 
directions, after the creatures which formed its food. 
Ichthyosaurus seems to have been very active, swimming 
about not only in the shallow seas, but also out into the open 
ocean and deep water. Plesiosaurus, on the other hand, 
seems to have preferred shallow water, where it lay lurking 
among the weeds, and concealed by them both from its 
enemies and its prey. From its ambush Plesiosaurus could 
dart forth its head, to seize with its sharp, recurved teeth 
some passing fish or cuttle, or from time to time raise it to 
the surface to draw air into its lungs. 
Now let us consider the structure of this reptile in refer¬ 
ence to that of others. If we know little or nothing about 
the ancestors of Ichthyosaurus, we know a great deal of those 
of Plesiosaurus, and can assign its position in the animal king¬ 
dom with some certainty. 
If we look at the bones in the paddle of Plesiosaurus (Fig. 8), 
we find that they are distinctly modified for swimming pur¬ 
poses : the bones are all flattened and placed close together, 
and were covered by a single sheet of membrane as in Ichthyo¬ 
saurus, so that there were no separate fingers. At the same 
time, we can see that the paddle is much more like the limb 
of a crocodile than is the paddle of Ichthyosaurus ; for the 
humerus is well developed, the ulna and radius are quite 
recognisable, as also are the wrist and palm bones ; after the 
latter come five rows of finger bones, never six or seven, as in 
Ichthyosaurus. 
An inspection of the paddle of Plesiosaurus, then, makes 
