18 ELEPHANTS. 



third ami fourth is there any '.arrangement of the anterior 

 cusps to form a transverse ridge. The first and second molars 

 (fig. 7 C), like those of the upper jaw, consist of two transversely- 

 arranged pairs of knobs and a posterior knob which is larger 

 than in the upper teeth. The last lower molar (fig. 10 A) has 

 a third ridge forming a sort of heel or talon, as it is called ; this 

 tooth, though much smaller, is remarkably similar to the molars 

 of some of the earlier forms oE Mastodon. 



The skeleton of Moeritherium is not well known, but some of 

 the most important points in its structure are: (1) the neck 

 is proportionated longer than in the later elephants in which it 

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

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

 are much expanded. The humerus also is rather different, 

 particularly at its lower end, the great 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 external nasal opening, its some- 



what 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. 



