TUSKS AND MOLARS 219 



the maxillae, and so forth. This state of affairs, together with 

 the presence of the huge tusks, has, as it were, pushed hack the 

 nasal orifices to near the top of the skull in a very Whale-like 

 fashion. As in the Cetacea, the nasal bones are limited in size, 

 and the premaxillae send up processes to join the frontals and 

 the nasals. There is a straight and somewhat slender zygomatic 

 arch, l)ut the orbit is not separated from the temporal fossa. The 

 malar bone is small, and, as in Eodents, forms the middle part 

 of the zygoma. This is not the case with most Ungulata. The 

 symphysis of the mandibles forms a spout-like rim. The scapula 

 has a narrow prescapular, but a very wide postscapular region. 

 The spine has a strong process projecting backwards from near 

 its middle ; this is a point of likeness to certain Eodents. Xo 

 Elephant has a clavicle. The most remarkable feature about 

 the fore-limb is the separation and crossing of the radius and 

 ulna. The arms of these animals are permanently fixed in the 

 position of pronation. The foot is short, and the bones of the 

 carpus are serially arranged. There are, however, traces of a 

 commencing interlocking of these bones in many forms. The 

 hind-feet are somewhat smaller than the fore-feet, and the tibia 

 and fibula are both developed. 



As to the teeth, this genus is to be distinguished from allied 

 forms by the presence of tusks in the upper ja-w only. I'hese 

 tusks have no bands of enamel such as characterise those of 

 Mastodon. They are incisors. There is, however, a trace 

 of the former enamelling in the shape of a patch at the tip, 

 which soon wears away. The molar teeth of Elephas are so 

 large that the jaws cannot accommodate more than at the 

 most two and a part of a third at a time. These are gradu- 

 ally replaced by others to the number of three, the replace- 

 ment of teeth suggesting that of the Manatee. Each molar is 

 deeply ridged, the interstices between the ridges being filled up 

 with cement. As the tooth wears away, therefore, the surface 

 continues to be flat. Each ridge consists of a core of dentine 

 surrounded by a coat of enamel. The number of these ridges 

 varies greatly from species to species. The Indian Elephant is 

 one of those which have the greatest number of plates in a single 

 tooth, as many as twenty-seven.^ Of the six molars which eventu- 



^ It must lie borne in mind that tlie teeth increase in complexity, those first 

 pushed up having the fewest plates. The first has only four transverse plates. 



