250 THE AMERICAN MUSEUM JOURNAL 
Professor Dames of Berlin show, however, that the neck was by no means 
as flexible as indicated by this restoration. This is proved by the character 
of the joints of the neck vertebrae, which are nearly flat instead of being 
ball-and-socket joints as in the neck of mammals and of most modern 
reptiles, or saddle-shaped joints as in birds. These flat joints, like those 
in the back of mammals, allow but a limited amount of motion at each 
joint, which must have been only partially offset by the great number of 
vertebrie in the neck of the Plesiosaurs. 
The name Plesio-saur or “near-lizard,” given to these animals about a 
century ago, indicates that they are more like the modern reptiles than are 
the “fish-lizards”’ or Ichthyosaurs found in the same geologic formations. 
But they are not related to lizards any more than to snakes, crocodiles or 
turtles, and the name of “Great Sea Lizards” which was given to them in 
the popular natural history works of fifty years ago is an unfortunate one, 
because there was in the Reptilian Era a third group of great marine rep- 
tiles, the Mosasaurs, which were in fact relatives of the lizards and resembled 
them in many respects, although lke Plesicsaurs and Ichthyosaurs, they 
were provided with swimming paddles instead of feet. Skeletons and 
restorations of Mosasaurs and Ichthyosaurs are exhibited on the walls of 
the east corridor near the elevator, and show the differences between these 
three types of great marine reptiles. 
We must suppose that Plesiosaurs were carnivorous, the sharp-pointed 
flaring teeth being adapted to seize a quick-moving prey rather than to feed 
upon slow-moving shellfish or upon seaweeds. But from the proportions 
of the body and the analogy with turtles we may suppose that they swam 
slowly and usually near the bottom, coming up on their prey stealthily from 
underneath instead of pursuing it through the water like the swift Ichthyo- 
saurs or the modern sharks and dolphins which these reptiles resembled. 
The long neck was too stiff for very quick movements, but would neverthe- 
less be of great assistance both in capturing prey and in reaching the surface 
to breathe, a necessity for all reptiles. It is common to find with Plesiosaur 
skeletons a considerable number of pebbles enclosed within the body cavity. 
Sometimes a peck of these pebbles are found — hard, round, with polished 
surfaces, and varying in size from a hen’s egg to a baseball. [t is prob- 
able that these pebbles assisted digestion, as is the case in many birds, 
the pebbles seeming to crush and grind the hard parts of the food in the 
gizzard. If so we must suppose that the prey of the Plesiosaurs contained 
hard parts for which this kind of crushing was necessary. It has been sug- 
gested that they preyed in part upon the squid-like baculites and belem- 
nites whose remains are exceedingly abundant in the same formations. 
