18 ELEPHANTS. 



Wall- is much shortened, (2) the hip-bones are narrow, while in the 



' later forms, owing to the great increase in size and weight, they 



case LM are mucn expanded. The hnmerus also is rather different, 



particularly at its lower end, the greater supinator ridge, so 



characteristic of the larger Proboscidea, being scarcely developed. 



On the other hand, the thigh-bone is extremely like that of a 



very small elephant. 



To sum up the primitive characters of Moeritherium : 



1. The skull differs little from that of an ordinary ungulate. 



2. There is a full set of three pairs of incisors in the upper, 



and only one pair wanting in the lower jaw. 



3. There is a canine on each side in the upper jaw. 



4. There are three premolars in the upper and lower jaws 



replacing milk-molars. 



5. The molars have only two transverse ridges and a small 



hind lobe ; each transverse ridge is composed of two 

 distinct cusps ; the third lower molar has also a heel 

 or talon. 



Some of the more important of the Proboscidean characters 

 are : 



1. The large size of the nasal opening, its somewhat 



backward situation, and the small size of the nasal 

 bones. 



2. The commencement of the development of air-cells in 



the bones of the back of the skull. 



3. The enlargement of the second incisors in both jaws to 



form tusks. 



4. The transversely ridged character of the molars. 



5. The spout-like anterior portion of the lower jaw. 



All these characters become much more marked in the next 

 stage, which is represented by Palaomastodon from the Upper 

 Eocene of Egypt. 



The genus Palaeomastodon (figs. 9-11, 13) is represented 

 by several species varying in size from an animal little 

 larger than Moeritherium to one nearly as large as a small 

 elephant, so that in the matter of size alone there is a great 

 advance in the direction of the modern elephants. In the 



