650 ANNUAL EEPORT SMITHSONIAN INSTITUTION, 1908. 



The earliest known proboscidians were discovered in the Egyptian 

 Fayiim, in beds of middle Eocene age. Their remains are also found 

 in the upper Eocene of the Fayum, but the Oligocene elephants are 

 as yet undiscovered. During the early Miocene the first migration 

 occurred into Europe and thence to the region of India and even as 

 far as North America, both of which were reached by the middle 

 Miocene. The Pliocene saw the elephants in their millenium, having 

 reached the widest dispersal and the maximum in numbers of species. 

 During Pleistocene times the Proboscidia covered all of the great land 

 masses except Australia, but were diminishing in numbers, and 

 toward the close of the Pleistocene the period of decadence began, 

 resulting in the extinction of all but the Indian and African elephants 

 of to-day. 



SUMMARY or THE EVOLUTION. 



The ph^^sical changes undergone by the race are also clearly shown, 

 as the paleontological series is very complete. These changes may 

 thus be summarized : Increase in size and in the development of 

 pillar-like limbs to support the enormous weight. Increase in size 

 and complexity of the teeth and their consequent diminution in num- 

 bers and the development of the peculiar method of tooth succession. 

 The loss of the canines and of all of the incisor teeth except the second 

 pair in the upper and lower jaws and the development of these as 

 tusks. The gradual elongation of the symphysis or union of the lower 

 jaws to strengthen and support the lower tusks while digging, cul- 

 minating in Tetrahelodon angustidens. The apparently sudden short- 

 ening of this symphysis following the loss of the lower tusks and the 

 compensating increase in size and the change in curvature of those 

 of the upper jaw. 



The increase in bulk and height, together with the shortening of 

 the neck necessitated by the increasing weight of the head with its 

 great battery of tusks, necessitated the development of a prehensile 

 upper lip Avhich gradually evolved into a proboscis for food-gath- 

 ering. The elongation of the lower jaw implies a similar elongation 

 of this proboscis in order that the latter may reach beyond the tusks. 

 The trunk did not, however, reach maximum utility until the short- 

 ening jaw, removing the support from beneath, left it pendant, as 

 in the living elephant. 



The change in the form of the skull developed pari passu with 

 the growth of the tusks and trunk, as it is merely a mechanical 

 adaptation to give greater leverage in the wielding of these organs. 

 It may readily be seen that these changes curiously interact upon one 

 another ; the result of the evolution of its parts being the development 

 of a most marvelous whole. 



