d curved claws on the feet, prove
the carnivorous habits of these dinosaurs. The well-finished joints,
dense texture of the hollow bones and strongly marked muscle-scars
indicate that they were active and powerful beasts of prey. They range
from small slender animals up to the gigantic _Tyrannosaurus_
equalling the modern elephant in bulk. They were half lizard, half
bird in proportions, combining the head, the short neck and small fore
limbs and long snaky tail of the lizard with the short, compact body,
long powerful hind limbs and three-toed feet of the bird. The skin was
probably either naked or covered with horny scales as in lizards and
snakes; at all events it was not armor-plated as in the crocodile.[4]
They walked or ran upon the hind legs; in many of them the fore limbs
are quite unfitted for support of the body and must have been used
solely in fighting or tearing their prey.

[Illustration: Fig. 10.--Hind Limb of Allosaurus, Dr. J.L. Wortman
standing to one side. Dr. Wortman is one of the most notable and
successful collectors of fossil vertebrates and was in charge of
the Museum's field work in this department from 1891-1898.]

The huge size of some of these Mesozoic beasts of prey finds no
parallel among their modern analogues. It is only among marine animals
that we find predaceous types of such gigantic size. But among the
carnivorous dinosaurs we fail to find any indications of aquatic or
even amphibious habits. They might indeed wade in the water, but they
could hardly be at home in it, for they were clearly not good
swimmers. We must suppose that they were dry land animals or at most
swamp dwellers.

_Dinosaur Footprints._ The ancestors of the Theropoda appear first in
the Triassic period, already of large size, but less completely
bipedal than their successors. Incomplete skeletons have been found in
the Triassic formations of Germany[5] but in this country they are
chiefly known from the famous fossil footprints (or "bird-tracks" as
they were at first thought to be), found in the flagstone quarries at
Turner's Falls on the Connecticut River, in the vicinity of Boonton,
New Jersey, and elsewhere. These tracks are the footprints of numerous
kinds of dinosaurs, large and small, mostly of the carnivorous group,
which lived in that region in the earlier part of the Age of Reptiles,
and much has been learned from them as to the habits of the animals
that made them. The tracks ascribed to carniv