THE early forms of reptiles, whose remains are chiefly known from Pennsylvania, gave rise to a diversity of crude-looking creatures which in the course of time led to an assemblage as powerful and important as any the world has ever seen. In the air, in the waters of lakes and rivers, in the sea, and on land, reptiles were to become rulers at least until the end of the Cretaceous period.1 During the hundred million years occupied by the Triassic, Jurassic and Cretaceous periods, they were without question the dominant animals in every domain, hence this long time, commonly known as the Meso-zoic, or ‘period of middle life,’ is also known as ‘The Age of Reptiles.’ Here were produced the most fantastic of nature’s creations, the most interesting forms, and the great company whose living descendants give but little indication of their former glory.
The name reptile means ‘creeping,’ but we shall see that these great reptiles were by no means merely creeping things. The simple amphibian ancestor which produced some unknown reptile started a stem that quickly sprouted to give the Ichthyo-saurs, Plesiosaurs and Mosasaurs as monsters of the sea; the pterodactyls in the air; crocodiles, turtles and tortoises, snakes and lizards, and the remarkable giants of the earth, the Dinosaurs.
Though little is known of the Carboniferous reptilian fauna, in the succeeding period, the Permian, there was quite a diversified representation, both of land-living and water-living forms. Amongst these, one or two will serve for description.
A HELMET-CLAD LIZARD WITH THREE EYES THE first of them comes from South Africa and is known by many specimens, the best of which is on public view at the Natural History Museum, South Kensington. Its name is Pareiasaurus, which can be translated as the ‘helmet-cheeked lizard.’ It may be pointed out here that the suffix ‘saurus ‘means in Greek ‘lizard,’ though ‘reptile ‘must generally be understood. This African form derives its name from the fact that the whole of the head is completely roofed by bone, except for the eye openings and for the comparatively large orifice (foramen) for the pineal, or third eye.
This last-named organ, which we have already mentioned,.
occurs in some fish, in the amphibians, and in many reptiles, chiefly the swimming kinds. The structure so far as we can judge it from living animals, was a primitive eye, with nervous connections, lens, and retina, but whether it had visual powers or not we do not know. In the living Sphenodon, a reptile with a very long history, this organ persists, but experiments have failed to reveal its function. In the purely aquatic forms it may have served as an eye, sensitive to movements and to light above the creature. At any rate, in the higher kinds of animals, the optical arrangement of the eye is lost and the opening in the bones of the skull is closed up. The structure is identifiable only as the pineal gland (a gland situated in the brain) which, in man, was considered by the early anatomists to be the seat of the soul.