ELEPHANTS 859 



the large muscles. In most of the bones there is during 

 growth an extraordinary development of air-spaces, which 

 communicate with the nasal passages. The supra-occipital 

 is very large ; the nasal bones are very short ; the zygomatic 

 arch is slender and straight, its anterior part is formed by 

 the maxilla, for the elephant differs from the typical 

 Ungulates in the fact that the jugal merely forms the 

 median part of the zygoma, and does not extend on to the 

 face. The lachrymal is also small, and placed almost 

 entirely within the orbit (cf. the Rabbit). 



The dentition is unique. The two upper incisors or 

 tusks are mainly composed of solid ivory ; the enamel is 

 restricted to the apex, and soon wears off. As the tusks 

 grow, their roots sink through the premaxillae into the 

 maxillae. There are no canines nor premolars. The 

 molars are very large, and the enamel is very much plaited, 

 forming a series of transverse ridges enclosing the dentine, 

 and united to one another by cement. Thus on the worn 

 tooth there are numerous successive layers of enamel, 

 dentine, and cement. Extinct forms show transitions 

 between this complex type and the horse's tooth. In a 

 lifetime there may be six molar teeth on each side of each 

 jaw, but of these only one, or portions of two, can find 

 space at a time. The series gradually moves forward as 

 the front parts are worn away and cast out. 



The brain is highly developed. 



The stomach is simple, and there is a large caecum. 



There are two superior venae cavae entering the right 

 auricle. The kidneys have several lobes, separated by 

 muscular partitions. 



The testes remain abdominal in position. 



There are two pectoral mammae ; the uterus is bi- 

 cornuate ; the placenta is non-deciduate and zonary. 



Elephas, ^~, now represented by the Indian Elephant (E. indicus), 



with parallel folds of enamel on the molars, and ears of moderate size, 

 and the African Elephant (E. africanus), with lozenge-shaped folds of 

 enamel, and very large ears. 



The mammoth (E. primigenius) belonged to the Pleistocene period, 

 and had a wide geographical range, occurring, for instance, in Britain. 



The genns Mastodon is represented by fossil remains in Miocene, 

 Pliocene, and even in Pleistocene strata, in Europe, India, and 



