Page:Popular Science Monthly Volume 87.djvu/243

Rh which flourished throughout the Mesozoic, but which are here represented in the climax of their evolutionary career. Some were huge headed forms, armed on the snout and above the eyes with horns like those of cattle and with a wide bony crest which protected the neck. These were quadrupeds of rhinocerine proportions, but of much greater size. Others were bipeds with a long tail which served to balance the body when running on land and was a very efficient propelling organ when stress of circumstance made it necessary to take to the waters for retreat. This second group was armor-and weapon-less, with a curious duck-like expansion of jaws, toothless in front but with a wonderful battery of more than two thousand teeth in the rear of the mouth. Occasional mummied carcases have been found which betray the defenseless condition of the scaly skin. Both of these groups were plant feeders, but a third sort, again erect on the hind limbs, bore teeth and claws which can only mean a rapacious flesh-feeder, doubtless the arch-enemy of the other two. These carnivores were represented by small, agile forms, and by others which were truly gigantic.

The dinosaur remains are pretty widely spread over the present area, the horned skulls generally occurring in hard concretionary masses of sandstone, many of which were collected and shipped to New

Haven and later to the National Museum in Washington, where the contained fossils were freed from the investing rock. Most of the