Page:Popular Science Monthly Volume 12.djvu/541

Rh the Glyptosauridæ, were protected by a highly-ornamented bony coat of-mail, and others were covered with scales, like recent lizards. A few resembled, in their more important characters, the modern iguana. The genera best represented in the Eocene are—Glyptosaurus, Iguanavus, Oreosaurus, Thinosaurus, Tinosaurus, and Saniva. Some of these genera appear to have continued into the Miocene, but here, as well as in the Pliocene, few remains of this group have been found. It is not improbable that some of our extinct Reptiles may prove to belong to Ryncocephala, but at present this is uncertain. The genus Notosaurus, from Brazil, has biconcave vertebræ, and some other characters which point to that group. No Dicynodonts or Theriodonts have as yet been found in this country.

The first American serpents, so far as now known, appear in the Eocene, which contains also the oldest European species. On the Atlantic border, the genus Titanophis (Dinophis) is represented by several species of large size, one at least thirty feet in length, and all doubtless inhabitants of the sea. In the fresh-water Western Eocene, remains of snakes are abundant, but all are of moderate size. The largest of these were related to the modern boa-constrictors. The genera described are Boavus, Lithophis, and Limnophis. The Miocene and Pliocene snakes from the same region are known only from a few fragmentary remains.

The Pterosauria, or flying-lizards, are among the most interesting reptiles of Mesozoic time, and many of them left their remains in the soft sediments of our inland Cretaceous sea. These were veritable dragons, having a spread of wings of from ten to twenty-five feet. They differed essentially from the smaller Pterodactyls found in the Old World, in the entire absence of teeth, showing in this respect a resemblance to modern birds; and they possess other distinctive characters. They have therefore been placed in a new order, Pteranodontia, from the typical genus Pteranodon, of which five species are known. The only other genus is Nyctosaurus, represented by a single species. All the specimens yet found are from essentially the same horizon, in the chalk of Kansas. The reported discovery of remains of this order from older formations in this country is without foundation.

The strange reptiles known as Dinosauria, which, as we have seen, were numerous during the deposition of our Triassic shales and sandstones, have not yet been found in American Jurassic, but were well represented here throughout the Cretaceous, and at its close became extinct. These animals possess a peculiar interest to the