To us by far the most interesting mammalian life is that found south of the mouth of the Neckar along the ancient stream Elsenz, where were deposited the lower 'sands of Mauer,' containing the lower jaw of the Heidelberg man and the remains of many animals of the period. The enumeration of this entire fauna is very important, as indicating the temperate climatic conditions which surrounded the first true species of man which has thus far been discovered in Europe. The discoverer, Schoetensack,(35) referred these mammals and the Heidelberg man to the First Interglacial Stage, and a similar opinion has recently been expressed by Geikie. The presence of the Etruscan rhinoceros would appear to point to such great antiquity, but the evidence afforded by this primitive animal is overborne by that of three mammals which are highly characteristic of Second Interglacial times; these are the straight-tusked or ancient elephant (_E. antiquus_), the lion, and the Mosbach horse. Excepting only the Etruscan rhinoceros, all these species frequenting the ancient stream Elsenz and deposited with the 'sands of Mauer' occurred also in the forests and meadows of the region now known as Baden, where the fossil mammal deposits of Mosbach near the Neckar are found. A similar mammalian life of a somewhat more recent time occurs in the river gravels of Süssenborn, near Weimar. The horses of Mauer, of Mosbach, and of Süssenborn[Q] were of much larger size and of more specialized character than Steno's horse of First Interglacial times. [Illustration: FIG. 45. Section of the valley of the stream Elsenz, near Heidelberg, showing the location of the Mauer sand-pit in which the Heidelberg jaw was discovered. An ancient layer of river-drift. Drawn by C. A. Reeds.] Thus the Heidelbergs, the first human race recorded in western Europe, appear in northern Germany early in Second Interglacial times, in the midst of a most imposing mammalian fauna of northern aspect and containing many forest-living species, such as bear, deer, and moose; in the meadows and forests browsed the giant, straight-tusked elephant (_E. antiquus_), which from the simple structure of its grinding-teeth is regarded as similar in habit to the African elephant now inhabiting the forests of central Africa; the presence of this animal indicates a relatively moist climate and well-forested country. The Etruscan rhinoceros differed from the larger Merck's form in the possession of relatively short-crowned grinding-teeth, adapted to browsing habits and a forested country; on the head were borne two horns; it was a long-limbed, rapidly moving type; the herds of bison and of wild cattle (urus) which roamed over the plains were now subject to the attack of the lion. [Illustration: FIG. 46. Sand-pit at Mauer, near Heidelberg, discovery site of the jaw of Heidelberg man. After Schoetensack. _a-b._ 'Newer loess,' either of Third Interglacial or of Postglacial times.