IX 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 back the 
nasal orifices to near the top of the skull in a very Whale-lhke 
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, but the orbit is not separated from the temporal fossa. The 
malar bone is small, and, as in Rodents, 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 Rodents. No 
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 Jaw only. These 
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 Hlephas 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- 
"Tt must be borne in mind that the teeth increase in complexity, those first 
pushed up having the fewest plates. The first has only four transverse plates. 
