[Illustration:  Fig. 179—­Rhamphorhynchus Bucklandi, restored.  Bath Oolite, England. (After the late Professor Phillips.)]

The Pterosaurs are wholly Mesozoic, ranging from the Lias to the Chalk inclusive; and the fine-grained Lithographic Slate of Solenhofen has proved to be singularly rich in their remains.  The genus Pterodactylus itself has the jaws toothed to the extremities with equal-sized conical teeth, and its species range from the Middle Oolites to the Cretaceous series, in connection with which they will be again noticed, together with the toothless genus Pteranodon.  The genus Dimorphodon is Liassic, and is characterised by having the front teeth long and pointed, whilst the hinder teeth are small and lancet-shaped.  Lastly, the singular genus Rhamphorhynchus, also from the Lower Oolites, is distinguished by the fact that there are teeth present in the hinder portions of both jaws; but the front portions are toothless, and may have constituted a horny beak.  Like most of the other Jurassic Pterosaurs, Rhamphorhynchus (fig. 179) does not seem to have been much bigger than a pigeon, in this respect falling far below the giant “Dragons” of the Cretaceous period.  It differed from its relatives, not only in the armature of the mouth, but also in the fact that the tail was of considerable length.  With regard to its habits and mode of life, Professor Phillips remarks that, “gifted with ample means of flight, able at least to perch on rocks and scuffle along the shore, perhaps competent to dive, though not so well as a Palmiped bird, many fishes must have yielded to the cruel beak and sharp teeth of Rhamphorhynchus.  If we ask to which of the many families of Birds the analogy of structure and probable way of life would lead us to assimilate Rhamphorhynchus, the answer must point to the swimming races with long wings, clawed feet, hooked beak, and habits or violence and voracity; and for preference, the shortness of the legs, and other circumstances, may be held to claim for the Stonesfield fossil a more than fanciful similitude to the groups of Cormorants, and other marine divers, which constitute an effective part of the picturesque army of robbers of the sea.”

Another extraordinary and interesting group of the Mesozoic Reptiles is constituted by the Deinosauria, comprising a series of mostly gigantic forms, which range from the Trias to the Chalk.  All the “Deinosaurs” are possessed of the two pairs of limbs proper to Vertebrate animals, and these organs are in the main adapted for walking on the dry land.  Thus, whilst the Mesozoic seas swarmed with the huge Ichthyosaurs and Plesiosaurs, and whilst the air was tenanted by the Dragon-like Pterosaurs, the land-surfaces of the Secondary period were peopled by numerous forms of Deinosaurs, some of them of even more gigantic dimensions than their marine brethren.  The limbs of the Deinosaurs are, as just said, adapted for progression