Wall-ease 
1 . 
Wall-ease 
2 . 
Table-eases 
1 - 4 . 
B. 
6 GUIDE TO THE FOSSIL REPTILES, AMPHIBIANS, FISHES. 
side to side, lengthened by a multiplication of the joints, and 
destitute of claws. There is no armour, except perhaps a 
partial covering of thin scales. The typical genus is 
Mosasaurus (“ Meuse-lizard ”) itself, so named because it was 
first found in the Chalk of Maastricht in the valley of the 
Meuse. This is represented in Wall-case 1, not only by a 
plaster cast of the skull and jaws of M. camperi, now in the 
Paris Museum (Pig. 1), originally described by Cuvier, but 
also by numerous other remains of the same species from 
Maastricht, including a fine piece of jaw presented more than 
a century ago by Dr. Peter Camper, the celebrated Dutch 
anatomist. Mosasaurus camperi must have been a very large 
animal, probably not less than 50 feet in length. Teeth and 
other fragments of Mosasaurus and allied genera ( Liodon , etc.) 
are also exhibited from the English Chalk. Instructive 
portions of the skeleton of a smaller Mosasaurian, Platecarpus 
(Fig. 2), are shown in slabs of Chalk from Kansas, U.S.A. A 
hind paddle of Tylosaurus, from the same formation and 
locality, illustrates the nature of the Mosasaurian limb. There 
is also from the Kansas Chalk a skull of Clidastes, a relatively 
small animal shaped remarkably like a snake, but with the 
usual paddles, and with a deepening of the spines of the 
hindmost tail-vertebrae, which suggests that it was originally 
provided with a vertical tail-fin. Fragments of jaws of a 
large Liodon from the Greensand of New Zealand indicate 
the wide range of the Mosasaurians in the Cretaceous sea. 
Order II.— ORNITHOSAURIA. 
True flying reptiles lived throughout the Secondary 
period, and are known by many nearly complete skeletons 
from the Lias of England and Germany, the Lithographic 
Stone (Kimmeridgian) of Germany, and the Chalk of Kansas, 
U.S.A. They form the Order Ornithosauria {“ bird-lizards ”), 
or Pterosauria (“ wing-lizards ”), and are commonly referred 
to as Pterodactyls, because Cuvier gave the name of Ptero- 
dactylus (“ wing-finger ”) to the first specimens when he 
originally described them and recognised their true nature. 
In these reptiles the skeleton is very light, and composed of 
hard, dense bone like that of birds of flight; while the 
vertebrae and limb-bones have well-fitting joints, and are 
hollowed to receive air from the lungs. The head is shaped 
like that of a bird, and similarly fixed at right angles to the 
neck. The brain is comparatively small, but in the arrange- 
