FOSSIL VERTEBRATES — REPTILIA O41 
instead of birds, as originally supposed. The bones are all 
hollow, and the whole skeleton was very light. There was an 
almost complete absence of the dermal armor that characterized 
the Stegosaurus; the whole lightness of the skeleton is incom- 
patible with the weight of such a covering, and it is likely that 
the animals sought safety in flight, where the former genus 
trusted to the impenetrability of its armor. The largest of the 
four genera, Camptosaurus, was about twenty feet long, and the 
smallest, Vanosaurus, was only three or four. The last genus is 
the lightest and the most birdlike of all the Dénosaurs. 
Dystropheus is the name given by Cope to the incomplete 
remains of a Dinosaur from the Triassic rocks of Utah. There 
is preserved only the portions of the hind limb but these show 
that the animal had only three functional digits on the hind foot 
and that it was closely related to the Camptosaurus. 
Teeth from the Potomac formation, evidently belonging to 
yhis group have been described by Marsh and Leidy as Priconodon 
and Paleoscincus. 
Euskelosaurus from the South African beds is too incomplete 
to be definitely placed anywhere, but is generally placed among 
these forms. 
Scelidosaurus is from the lower Lias of Dorsetshire in England. 
It was very similar in many respects to Stegosaurus, having the 
same quadrupedal locomotion and the same solid form cf the 
bones but the dermal armor was reduced to a single row of 
small ossicles down the median line of the back. The whole 
form was nearly twelve feet long. 
Agathaumus from the Upper Cretaceous of Wyoming, is one 
of the most peculiar of this peculiar group of animals; with the 
same bodily characters of the trunk as the Stegosaurus, minus the 
dermal plates, the interest of the form centers in the enormous 
development of the protective armature of the skull. The bones 
of the posterior cranial region were developed as an enormous 
cape that extended back over the shoulders; around the edges 
of the cape there was a series of smaller bones. The frontal 
portion of the superior aspect of the skull was protected by the 
