MAMMALIA. 331 



remains of those supposed new species, before we can admit 

 the numbers that have been described ; many of the species 

 may be only varieties depending on sex and other causes. 



The genus ElepJias has the upper jaw armed with two 

 enormous tusks (fig. 241), which are, in fact, greatly- 



2 3 



FIG. 242. Teeth of Elephants. 1. E. africanus, 2. E. indicus. 3. E. primigenius. 



developed incisor teeth, that grow upwards in a curved 

 direction ; the molars are one or two in number, in each 



FIG. 243. Elephas primigenius. 



side of both jaws. They are composed of plates of dentine 

 and of enamel, united by a third, or cortical substance ; the 

 lines of enamel present a different mode of arrangement in 

 the African, Indian, and fossil species, as shown in the 



