640 SIIB DMICES, IFO SIC QIOVEIN IES 
while in others the hind limbs were nearly as large in proportion 
to the front limbs as in the 7heropoda,; the feet were armed, in 
the majority of cases, with flat claws, or hoofs. The dentition 
shows that the animals were herbivorous in diet, and the mouth 
is, in some fons). (erowded full Vol teeth. 9 Mhisyenoupy eid 
not develop the enormous size of the preceding group, but 
sought protection in the development of a bony armature that 
rendered them, in many cases, safe from the attacks of the car- 
nivorous forms. 
Stegosaurus.—Vhe jaws were furnished with teeth in the pos- 
terior portion only, the premaxillaries being edentulous and 
probably covered with a horny beak that served the animal in 
gathering the plants which formed its food. The teeth were 
flattened sideways, and the crowns were serrated; the lmbs, 
bones, and the vertebrz were solid; the fore and hind limbs 
were of the same size; the neural processes of the dorsal ver- 
tebree were quite high, and supported the ribs from near the 
apex; the feet were plantigrade, and the toes terminated in 
broad, hooflike claws. The most remarkable thing about the 
form was the fact that there were developed in the skin of the 
back and sides great, broad plates of bone that possibly stood 
up as a median ridge along the back. All the known specimens 
are from the Upper Jurassic of Colorado and Wyoming. 
Camptosaurus, Laosaurus, Dryosaurus, and Nanosaurus are all 
from the same horizon and the same localities as Stegosaurus. 
They resemble that form in the arrangement of the pelvis, the 
bones of the skull, and all the essential features of the group, 
but differ in many external characters, The hind limbs are 
much larger than the fore limbs, and seem to have monopolized 
the function of progression; the fore feet are very small, and 
could only, under peculiar circumstances, have served as organs 
of locomotion. ‘There were five functional digits on the fore 
feet and only three on the hind foot, so that the tracks would 
have been the same as those of a large bird, and it is very prob- 
able that the tracks in the Triassic sandstone of the eastern part 
of the United States may be tracks of these or of related forms, 
