EXTINCT FAUNAS OF THE MOHAVE DESERT 257 



antlers. A large four-tusked mastodon is known by numerous frag- 

 ments and occasional complete bones or large pieces of tusk. 



Next to the horses the most numerous of the hoofed animals are the 

 camels. They are known by at least three types. One is a small form of 

 the genus Procamelus. A second and very large type probably belongs 

 to the genus Pliavchenia. A third form with very large long limbs, a 

 larger animal than the living camel, is possibly to be referred to the 

 genus AUicamelus. Other genera may be present in the collection. 



Of the remaining fauna, the rodents are represented by rabbits. 

 The carnivores are known by at least eight species, including three 

 large cats, at least one of which is a sabre-tooth with the greatly de- 

 veloped upper canine teeth. Two others may belong to the true cats, 

 represented by the modern puma and wild cat, without the saber-like 

 upper teeth. The dogs include one small form similar to the fox. A 

 second tvpe, Tephrocyon, one of the most characteristic animals of this 

 horizon, is a form considered by many to be possibly the ancestor of the 

 modern dogs and wolves. The most abundant creatures of the dog 

 group are found in one or two representatives of the genus Aelurodon, 

 very large, very heavy-jawed animals, much larger than any modern 

 wolves, and even greatly exceeding the extinct dire wolf, now so well 

 known by abundant skeletons from the asphalt deposits of Eancho La 

 Brea. These animals were evidently not rare. They probably lived 

 off the herds of large ungulates, sometimes bringing down a live animal, 

 sometimes robbing the smaller wolves and the big cats of their prey. 

 Their unusually massive jaws and teeth seem built to serve as bone 

 crushers, and there can be little doubt that* the general state of dismem- 

 berment and destruction of all skeletons, and the absence of satisfactory 

 paleontologic materials in the Barstow formation, is due in large part 

 to the destruction of these scavengers. 



Birds are, known in the Upper Miocene beds by a few fragments 

 representing an owl. Eeptiles are represented by numerous fragments, 

 and several nearly perfect skeletons of a large tortoise resembling in 

 many respects the living desert tortoises of the Mohave. 



The fauna of the Upper Miocene is as a whole that of an open 

 country affording fairly abundant grass and herbage, and evidently 

 better watered than the Mohave Desert of the present day. The nu- 

 merous remains of grazing horses of the Merychippus type, the presence 

 of mastodons, oreodons, of many deer-antelope, a considerable variety 

 of camels, and a wild pig all indicate that grass and other nutritious 

 vegetation must have been more abundant than at present. The rela- 

 tively small representation of oreodons, and of browsing horses like 

 Hypohippus, and the presence of large tortoises are possibly to be cor- 

 related with open semi-arid character of the country. 



That small bodies of water were present at times in this area is 



VOL. LXXXVI. — 18. 



