JR. S. Lull — Evolution of the Elephant. 201 



elephants found therein seem almost without exception to have 

 entered from Africa by way of Gibraltar. The great ranges 

 of mountains in the new world may have influenced somewhat 

 the trend of migration, but were crossed by the proboscidians 

 at will. 



Vegetation does constitute a most effective barrier, especially 

 in the case of the tropical jungle of central America. During 

 the Pliocene, as we shall see, after the land bridge was estab- 

 lished, intercommunication between the two Americas was 

 very free. In the Pleistocene, however, this migration of large 

 quadrupeds gradually ceased, so that in spite of the great 

 abundance of mammoths and mastodons in North America 

 none attained a foothold south of the Mexican plateau. To-day 

 the jungle is absolutely impenetrable for all of the larger 

 mammals except such as may be at least partially arboreal in 

 habits. 



The migrations were forced, not voluntary, for it would 

 appear that the mighty elevations of Asia beginning in late 

 Miocene times and the consequent alternations of moist and arid 

 climates, with a strong tendency toward the latter, has caused 

 these great animals to disperse themselves from the rising high 

 lands of central Asia into the more stable low lands. In these 

 forced wanderings the land bridge between Asia and Alaska 

 was again and again discovered and crossed by the migrating 

 hordes. 



The first appearance of the proboscidians is in the Middle 

 Eocene beds of the Egyptian Fayum district. There we find 

 in Mosritheriuni, the most primitive type, the forerunner of 

 the race. Of the extent of the geographical range of Mceri- 

 therium and of its successor, Palmomastodon, we know 

 nothing further than that they have only been found within 

 the Fayum. 



During the Oligocene the proboscidians seemingly remained 

 in Africa, though of this we have no record. Early Miocene 

 deposits of Mogara, which lies northwest of the Fayum some 

 five days' journey, about 75 miles,, give us the remains of 

 Tetrdbelodon angustidens, the next known type in the evolu- 

 tionary series. From Tunis again this species is reported, 

 being what Professor Deperet calls the ancestral (ascending 

 mutation) race of T. angustidens, jpigmoeus. This race is also 

 reported from the sands of Orleans and from the Burdigalienne 

 of Agles (Aglie, Italy). Thus it seems as though Tetrdbelodon 

 angustidens, the form with the maximum development of 

 symphysis, were the one to make the exodus from Africa, not 

 as the children of Israel did, by way of the northeast, but by 

 the land bridge Connecting Tunis with Sicily and the latter 

 with Italy, and thence, by way of Greece to Europe and Asia. 



Am. Jour. Sci.— Fourth Series, Vol. XXV, No. 147.— March, 1908. 

 14 



