EVOLUTION OF ELEPHANTS 337 



Continuation, e. Mastodon americanus, Pleistocene, Nebraska. /. Elephas hayi 

 Pleistocene, Nebraska. g. Elephas columbi. Pleistocene, Nebraska. e and g modi 

 fied after Osbom. 



ment of the molar as shown in Hving elephants. This, 

 proceeding from the nipple tooth of the mastodon, its thick 

 cross-ridges traversed by wide depressions, has passed 

 through the stage exhibited by the teeth of Stegodon, having 

 an increased number of ridges, while a good part of the 

 intervening spaces is now partly filled up with dental ce- 

 ment. This change is accentuated in the true elephant 

 molar with still deeper ridges, between which the much 

 greater amount of cement almost serves to obliterate the 

 intervals.* 



The German zoologist. Dr. W. Soergel, finds that the 

 form of the skull and tusks of the American Elephas im- 

 perator correspond fully with those of the Old World species, 

 meridionalis, trogontherii, and primigenius, the great size 

 of the imperator also indicating its formal relationship to 

 these. The molars of imperator represent essentially the 

 stage of development shown in Elephas trogontherii meri- 



*See A. Smith Woodward, "A Guide to the Fossil Mammals and Birds in the Depart- 

 ment of Geology and Palaeontology in the British Museum," London, 9th ed., 1909, pp. 

 65-60. 



Continuation. e. Stegodon. f. Elephas hayi. g. Elephas imperator. 



