Mongolia

The 1925 expedition of 4o men comprised the following branches of science : palaeontology, geology, palaeobotany, archaeology, to pography, zoology and photography. The foreign staff included 12 Americans and 2 British ; in the native staff there were 26 Chinese and Mongols, some being highly trained assistants. With so many branches of science represented it was improbable that all the men could find work in the same place at the same time. Therefore, the expedition was divided into four units, each with a car complete with its own driver, interpreter, cook and camp gear; any unit could leave the base camp and maintain itself inde pendently for several weeks if necessary. As a matter of fact the expedition was almost continually divided except on long marches to new localities ; frequently there were four camps from 20 m. to ioo m. apart.

General Survey.

It became evident that the first season must be devoted to a general survey of several thousand miles of country to locate and appraise its value for the especial purposes of the expedition without attempting exhaustive work in any of them. The next year could then be one of intensive study, the amount of time to be devoted to each locality be carefully planned in advance, and the staff adjusted accordingly. Since the main object of the expedition was to test the theory of central Asia as the chief theatre of mammalian evolution and distribution, palae ontology was most important during 1922-23.

Contrary to expectations, rich fossil deposits were discovered immediately. Four days after starting in 1922 it was found that the main trail between Kalgan, China and Urga, the capital of Mongolia, which had been traversed by several geologists, runs directly through three rich fossil beds—one Oligocene and one Eocene, of the age of mammals, and one Cretaceous, of the age of reptiles. The palaeontological work of the expedition, which was carried on under the direction of Walter Granger, "revealed the high central Asiatic plateau as the home of most of the terres trial dinosaurian reptiles of Upper Jurassic and of Cretaceous time. In brief, these discoveries establish Mongolia as a chief center of northern terrestrial life-history from the close of the Jurassic time onwards to the very close of Pleistocene time" (Osborn).

Since the middle of the age of reptiles, Mongolia has been con tinuously a high, dry continent. As a result, fossils "revealed especially the hitherto unknown high continental life of Cretaceous and Tertiary times" and showed that Gobia, as Grabau has named this ancient central Asian continent, was then sparsely forested, with limited rain supply and luxuriant with life, although it is now one of the most arid and inhospitable regions of the world. It was "extremely favourable to the evolution of reptiles, mammals, insects and plants hitherto known only along the Cretaceous shore lines of Europe and the Cretaceous sea-borders of the centre of America" (Osborn).

Dinosaur Eggs.

Among the several thousand fossil speci mens obtained it is difficult to select those of first importance scientifically, but in popular interest the dinosaur eggs stand fore most. These were discovered among dinosaur remains in a rich deposit almost in the centre of Mongolia near a well known to the Mongols as Shabarakh Ussu, the "Place of the Muddy Wa ters." The beds consist of fine red sandstone of Lower Cretaceous age and are extremely rich in skulls and skeletons of a hitherto un known dinosaur, Protoceratops andrewsi. Bits of shell were dis covered in 1922 but were not recognized as dinosaurian. The fol lowing year, on July 13, George Olsen found the first complete eggs. Three had broken out of a small sandstone ledge and lay exposed. Other shell fragments were partially embedded in the rock; just under the shelf were the projecting ends of two more eggs. Subsequently the block was found to contain 13 eggs in two layers lying with the ends pointing toward the centre, exactly as they had been left by the dinosaur when she covered them with sand for the last time millions of years ago. The skeleton of a small dinosaur was found, lying 4 in. above the eggs in the loose sediment on top of the rock. The specimen represented a tooth less species, Oviraptor philoceratops. It is possible that this little dinosaur existed by feeding on the eggs of its relatives and was about to rob the nest when it was buried by a sudden sand storm. The eggs first discovered are 8 in. long by 7 in. around. They are rather more elongate and flattened than those of modern reptiles and differ greatly in shape from the eggs of any known bird, living or fossil. The dry country and the loose, extremely fine, sand probably explain how such delicate objects as eggs were so beautifully preserved. After they had been deposited in a shallow "nest" scooped out of the sand the dinosaur covered them with a thin layer of sediment and left them to be hatched by the warmth of the sun. In a sudden wind storm, many feet of sand might have been heaped upon the eggs. Air and sun were thus cut off and incubation abruptly ceased. The weight of sediment eventually cracked the shells and the liquid contents ran out. Si multaneously the fine sand sifted into the interior forming the solid cores which are present in all the specimens. The loose sediment of the entire region was eventually consolidated into red-sandstone, the matrix in which all the eggs are enclosed. Two of those from the original discovery were somewhat broken ex posing the delicate skeletons of embryonic dinosaurs. It is prob able that other eggs contain the bones of unhatched young, for there were found several skulls of baby dinosaurs which evi dently had been out of the egg only a few days before death.