142 EXTINCT MONSTERS. 
twenty feet radius above the water. Then plunging into the 
depths, naught wouid be visible but the foam caused by the dis- 
appearing mass of life. Should several have appeared together, 
we can easily imagine tall, flexible forms rising to the height of the 
masts of a fishing-fleet, or like snakes twisting and knotting them- 
selves together. This extraordinary neck—for such it was—rose 
from a body of elephantine proportions. The limbs were 
probably two pairs of paddles, like those of Plesiosaurus, from 
which this diver chiefly differed in the arrangement of the bones 
of the breast. In the best-known species twenty-two feet 
represent the neck in a total length of fifty feet. This is Elas- 
mosaurus platyurus (Cope), a carnivorous sea-reptile, no doubt 
adapted for deeper waters than many of the others. Like the 
snake-bird of Florida, it probably often swam many feet below the 
surface, raising the head to the distant air for breath, then with- 
drawing it, and exploring the depths forty feet below, without 
altering the position of its body. From the localities in which 
the bones have been found in Kansas, it must have wandered 
far from land; and that many kinds of fishes formed its food 
is shown by the teeth and scales found in the position of its 
stomach.” 
But to return to the sea-serpents. Mosasaurus is now known 
to have been a long slender reptile, with a pair of powerful 
paddles in front, a moderately long neck, and flat pointed head. 
The tail was very long—flat and deep—like that of a great eel. 
Mosasaurus princeps is computed to have been seventy-five to 
eighty feet long. Clidastes was another genus of long and slender 
shape, one species of which reached a length of forty feet. Some 
forms of sea-serpent had sclerotic plates in the eye, such as we 
found in the fish-lizard, or Ichthyosaurus (p. 46), but the 
announcement that their bodies were protected by bony plates 
has turned out to be a mistake, and the supposed plates really 
belonged to the eye. 
Leiodon proriger (Cope) was abundant in the old North 
