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In 1923 the expedition discovered about 25 eggs, whole or in parts, and, in 1925, 4o more. That year produced by far the largest and finest eggs, as well as the smallest, representing several species and genera. One type, probably laid by a small carnivorous dinosaur, is not more than 5 in. long, is very elongate and has an extremely thin, smooth shell.
There were also bits of egg-shell probably representing one of the larger iguanodont, duck-billed dinosaurs from another region in Mongolia which awaits further exploration. Only in these two localities of the world have dinosaur eggs been dis covered up to 1928, with the possible exception of a few some what doubtful shell fragments from Rognac, southern France. Shabarakh Ussu also yielded 75 skulls and 54 dinosaur skeletons. probably the finest preserved material of the sort. One superb series of Protoceratops skulls represent almost every stage of growth from the newly hatched young up to very old individuals.
Another discovery, second only in popular interest to the dinosaur eggs, was the skull and parts of the skeleton of the gigantic aberrant rhinoceros Baluchitherium, the largest land mammal known to have existed. First information of this extraordinary beast was given by C. Forster Cooper of Cambridge university, who found a neck vertebra and foot bones in 1911 in Baluchistan. But it was not until the discovery in Mongolia of an almost complete skull in 1922 that the real char acteristics of the animal became known. In 1925 were found the four legs and feet of another individual that evidently had been trapped in quicksand and buried alive. It is estimated that the Baluchitherium stood 13 ft. high at the shoulders, that it was about 24 ft. long and that with its prehensile upper lip it could pull down tree branches 22 ft. in the air. It lived during the Oligocene period of the age of mammals and appears to have been confined to Asia.
From the standpoint of pure science possibly the most important specimens obtained by the expedi tions were seven Cretaceous mammal skulls found at Shabarakh Ussu in the same formation which contained the dinosaur eggs. They represent the oldest truly placental mammals known. They
were not larger than a small rat and crawled about in the middle of the Cretaceous era, the closing period of the age of reptiles, when dinosaurs still flourished. They may be regarded as the first attempt of nature to establish the insectivorous, herbivorous and carnivorous groups of mammals which were to become the dominant creatures of the earth.
The geological work of the expedi tions yielded most important results, the chief among them prob ably being the unravelling of the hitherto unknown major elements of geologic history of the Mongolian region and the working out of a fairly complete geologic column. It was learned that the structure of the Mongolian plateau consists of two great series of formations, separated by a profound unconformity. Those below the unconformity form a floor of ancient complex rock upon which the later sediments rest ; many of these are fossil bearing. The geologists identified and described an enormous granite bathylith or underlying floor. This is not only important to "pure science" but it supports the inference that valuable min eral deposits are more likely to be found about the margins of the bathylith than in the area of broad exposure. The region has a basin-like character. There have been several mountain-making periods, several erosion periods and several revivals of volcanism.
The Gobi is essentially a rock desert with a very thin veneer of shifting sand and much bare rock. Interpretation of the strata in dicates that this region has been continuously a continental area since early Mesozoic times; the sediments deposited since are all of continental type and not marine, being either fluvial, lacustrine or aeolian.
The reading of the history of climatic changes is one of the most important and interesting results of the expeditions and is the most extensive effort of its kind yet attempted in central Asia. The results achieved by Huntington in his study of the climatic changes of Pleistocene and recent time in other parts of Asia stand confirmed. Evidence is conclusive that this region has been arid and semi-arid in its climatic habit for many millions of years, but that there have been cycles of greater and less aridity.