The skull, hitherto unknown, was obtained by the Amherst College Expedition to Patagonia and its description by Professor F. B. Loomis is anxiously awaited. In advance of that, he has published a brief account, with a figure. This skull was long and narrow, with very short facial region and nasal bones so shortened that the nasal canal passed almost vertically down through the head, as in the elephants, and there must have been a considerable proboscis. Despite this great modification, the skull was plainly of the †toxodont and not of the proboscidean type. The legs were extremely massive and the fore legs were considerably shorter than the hind, with such a difference in length that the head must have been carried low, as in the Pampean †Toxodon. The upper arm and thigh were much longer than the fore-arm and lower leg respectively. The humerus was immensely broadened, especially the lower end, and the processes for muscular attachment were extremely prominent. The femur was long, with broad and flattened shaft, and had no trace of the third trochanter, quite strongly resembling the thigh-bone of an elephant, which, as we have repeatedly seen, is the type more or less closely approximated by all of the very heavy ungulates. In the standing position, the femur was in nearly the same vertical line as the tibia and the whole leg must have been almost perfectly straight, with the knee-joint free from the body. The short and massive fore-arm bones were coössified, at least in some individuals, as were the equally heavy bones of the lower leg, the fibula being exceptionally stout. Little is known of the feet, but that little renders probable the inference that they were short, columnar and five-toed.
The Eocene representatives of the Pyrotheria are known only from very fragmentary material. †Propyrotherium, of the Astraponotus Beds, was smaller than the Deseado genus and still smaller was †Carolozittellia of the Casa Mayor, which was not so large as a tapir. In the latter the molars were of the same type as in the succeeding forms and small tusks had already begun to develop. The older Eocene genus †Paulogervaisia was probably a member of this suborder; if so, it shows that the molars with transverse crests were derived from quadritubercular teeth, just as happened in the Proboscidea and several other ungulate groups.
CHAPTER XIII
HISTORY OF THE †LITOPTERNA AND †ASTRAPOTHERIA
Besides the four well-defined groups which make up the †Toxodontia (or †Notoungulata) there are two other extinct orders of indigenous South American ungulates, which remain to be considered. These did not have the exceptional development of the auditory region of the skull which characterized the †Toxodontia. The best known and most important genera of the †Litopterna are listed in the following table:
†LITOPTERNA. †Litopterns
I. †Macrauchenidæ.
†Macrauchenia, Plioc. and Pleist. †Scalibrinitherium, Paraná. †Theosodon, Santa Cruz. †Cramauchenia, Patagonian. †Protheosodon, Deseado.
II. Proterotheriidæ.
†Epitherium, Monte Hermoso. †Diadiaphorus, Santa Cruz and Paraná. †Proterotherium, do. †Thoatherium, Santa Cruz. †Deuterotherium, Deseado. † Prothoatherium, do.