the fossil records, but there are many other examples of similar import among other early animals. [Illustration: FIG. 61.—_Mesosaurus_; restoration of skeleton. (After McGregor)] The age of the South American proganosaurs is now believed to be lower or lowermost Permian, like that of the African _Mesosaurus_; possibly, however, the age first described to _Stereosternum_ (Carboniferous) may be correct. The known skeletons are all small, none exceeding a few feet in length. The skull, as shown in the figure by Dr. McGregor, is elongate, and its teeth are extraordinarily so, and very slender. The external nostrils are situated close to the eyes; and no sclerotic bones have been discovered. There are small teeth in the bones of the palate. The neck is elongate, composed of ten or twelve vertebrae. The trunk also is long and slender, and the tail is not only long, but also much flattened or compressed. All these are very characteristic of water life. The limbs, however, show a much less complete adaptation for swimming—not much more so in fact than do those of the living Crocodilia. The upper arm and the thigh bones are relatively long, while those of the forearm and the leg are shorter than among terrestrial reptiles, the first indication of swimming habits to appear in crawling animals. The digits are not much elongated, and they have no additional finger bones, save perhaps in a lately discovered form in Africa, in which Dr. Broom reports supernumerary bones in the fifth or “little” toe.[3] The fingers and toes have only blunt terminal bones, that is, they were not distinctly clawed, and they were probably connected with each other by a membrane, as in a frog’s foot. This webbing of the feet is probable, not only because of the positions in which the bones have been found, but also because of the great length of the “little” toe, which is the longest in the foot, a character quite abnormal for a land reptile and quite characteristic of certain aquatic mammals, like the seals and sea-otters. There is a strong sacrum of two vertebrae, however, the pelvis and hind legs being connected with the spinal column firmly, clearly proving that, like the crocodiles, the proganosaurs had by no means lost their land proclivities. [3] An additional phalange has also been observed in the fifth toe of a South American species.