1900.] Osborfi, Phylogeny of the Rhinoceroses of Europe. 243 



evolution differs from that of the American A. platycephalum as 

 shown in the diagram above (Fig. 8) ; other resemblances, how- 

 ever, are so strong that one is tempted to consider the possibility 

 that these animals belong to the same Aceratherine race which is 

 distinct from, but contemporary with the Diceratherine race. A 

 fossa representing the vestige of the postvallum in m* is seen in 

 these specimens, also in A. platycephalurn. 



2. Upper Oligocene Stage. 

 St. Gerand-le-Puy, Gaillac, Gan/iat, Randan, Eckingen, {Utm). 



A. lemanense Pomel. — This well known species is represented 

 by superb materials in Paris, Lyons, Munich, Stuttgart. These 

 specimens represent different (early or primitive and later) stages 

 of development ; some are less progressive and probably of Mid- 

 dle Oligocene age, others are more modernized and probably of 

 Lower Miocene age, but in all the premolars and molars are far 

 more advanced than in A. filholi. 



Sexual differences are pronounced as in the Dicerather- 

 iinae and Rhinoceroses generally ; the females have small canine 

 tusks and long very narrow or slender nasals ; the males have 

 large tusks and rudimentary rugosities or horn supports on the 

 sides of the extremities of the nasals. Adaptive radiation is also 

 marked and probably certain collateral species are given off from 

 the direct line. 



All these animals are readily distinguished from the Dicer- 

 atheriinse by much larger size. 



General Distinctions of Teeth. — Lower canines lance-shaped, lenticular in 

 section ; first lower premolar small, usually present; superior premolars with 

 crista, producing a medifossette upon extreme wear ; large antecrochet ; premo- 

 lars 2-4 with complete crests, which in the more primitive stages unite in 

 extreme wear ; an internal cingulum. Molars with strong antecrochet, becom- 

 ing stronger in wear ; with crista becoming weaker in extreme wear ; crochet 

 also becoming weaker with extreme wear ; metaconule fold becoming stronger 

 with wear ; protocone small ; postfossettes indicated in both m^ and m^, 

 with internal cingulum reduced or confined to median valley. Measurements : 

 pmi-m' = 265. 



Effect of age upon molar pattern. — It is extremely important to 

 observe that, exactly as recorded above in the Diceratheriince, 



