234 THE MAMMALIA. 



of these tubercles become more or less rubbed off 

 with age. Only in some cases are the furrows 

 between the ridges of the tooth somewhat filled with 

 cement. These differing varieties and intermediate 

 forms have obviously proceeded from the earlier 

 mastodons, and in order to simplify the arrange- 

 ment have been classed as the genus Stegodon. 

 Their home was chiefly in Italy, whence they 

 spread abroad as far as Japan. 1 The discovery of 

 their remains in the Japanese Archipelago is a 

 proof that these islands did not lose their connection 

 with the continent till comparatively recent times. 

 These teeth prepare us for the molar of the 

 true elephant, the latest form of the group. It 

 originates and indeed not in theory but in the 

 actual transition forms up to the living species 

 by the ridges continuing to become steeper, drawing 

 closer to one another, and sinking down almost to 

 the root of the tooth, and by these furrows be- 

 coming filled with cement, which thence covers the 

 whole outward surfaces of the tooth. The enamel 

 parts of the still unused tooth although in form 

 and extent extraordinarily changed nevertheless 

 show the same connection as in the species from 



1 Naumann, Ueber japanische Elephanten der Vorzeit, 

 Palceontographica, vi. 1882. 



