676 SCIENCE PROGRESS 



but when the Lower Miocene beds are reached, Proboscidean 

 remains are abundant, and we find them not only in African 

 but also in European and probably Asiatic and American 

 localities, the group having become widely spread since the 

 Upper Eocene. In the Lower Miocene deposits of Europe two 

 genera, Tetrabclodon and Dinotherium, are found, of which only 

 the first is at present known in Egypt, where remains have 

 been found at Mogara and in the Wadi Faregh. In this 

 animal, which is as large as an elephant, the skull is practically 

 the same as that of the later Elephants ; the tusks are now 

 very large, though they are still directed somewhat downwards, 

 and have a band of enamel on their outer side. The milk 

 molars, as in the earlier forms, are still replaced by premolars ; 

 but these are soon pushed forward and shed through the great 

 increase in size of the permanent molars. Of these the first and 

 second, though large, still have crowns with only three trans- 

 verse ridges ; the third molar, on the other hand, is still more 

 enlarged, and its crown maybe made up of five or six transverse 

 crests ; it is in fact so large, that when it is fully cut, not only 

 the premolars but also the first molars are displaced, there 

 being no room for them in the jaw. The anterior part of the 

 mandible, with the procumbent incisors, has now attained an 

 extraordinary length, projecting still farther beyond the skull 

 than in Palceomastodon ; in fact in this genus we have the 

 culmination of the specialisation in this direction, and the long 

 straight snout must have presented a remarkable appearance, 

 the animal having resembled an elephant in which the lower 

 jaw was so elongated that it could reach the ground, and was 

 covered with the fleshy snout, the end of which alone was free. 

 So far as the Egyptian deposits are concerned, this is the last 

 of the Proboscideans found ; but it may be permitted to give 

 a short summary of the subsequent changes which ended in the 

 evolution of the modern genus Elephas. During the Miocene 

 the long mandibular symphysis — probably because it had 

 attained an unwieldy length — became rapidly shortened up, 

 leaving the upper lip and snout free, as the movable proboscis 

 so characteristic of the group. Tetrabelodon longirostris, of the 

 late Miocene, represents a stage in this process. In this animal 

 the symphysis is comparatively short, and although the two 

 lower tusks attain a considerable size, they certainly could 

 not reach the ground. At the same time the number of ridges 



