HORNLESS EXTINCT FORMS 259 



name denotes, 1 had also canines and, in one species, six incisors 

 in the lower jaw. This Aceratherium had, moreover, four toes in 

 the fore-feet. In the Miocene and later the Ehinoceros existed in 

 Europe and America. There was even a purely northern form, 

 the Rli. tichorhinus, which possessed a woolly covering and had 

 the same range as the Mammoth. This Ehinoceros was two- 

 horned. 



The post-Pliocene and European Elasmotherium was a colossal 

 rhinocerotine creature. This great beast had two horns and a 

 body 15 feet long. Its limbs are not known, and as the teeth 

 are different from those of Rhinoceroses in general, it may not 

 have belonged to this group at all, though Osborn is inclined 

 to derive it from Aceratherium, admitting at the same time that 

 the evidence is " decidedly slender." The teeth in fact are like 

 those of a Horse in being hypselodont and prismatic in form. As 

 to the two horns, they were apparently not exactly like those of 

 typical Ehinoceroses ; there was an enormous horn posteriorly, 

 supported on a huge boss of bone, and in front of this a roughened 

 spot suggests a smaller or at least a much more slender horn. 



It is important to notice that fossil Ehinoceroses belonging to 

 the restricted genus Ehinoceros were in Europe invariably two- 

 horned ; it is only in India, where they still exist, that one-horned 

 forms are met with in a fossil state. 



The Ehinoceroses of America were mostly hornless. Dicera- 

 therium is an exception ; but in many cases it had two parallel not 

 successive horns, and these were, to judge from the slight promi- 

 nences, but feeble in development, and perhaps hardly exactly 

 comparable with the formidable weapons of the Old- World forms. 

 Aceratherium tridactylum, with indications of paired horns, may 

 be ancestral to Diceratherium. The American forms have weak and 

 slender nasals in correspondence with the absence of horns ; the 

 sagittal crest is retained in contradistinction to the great flattened 

 surface of the skull in the horned Ehinoceroses. Aceratherium of 

 both divisions of the globe probably represents the ancestral group 

 of the horned and the hornless forms. This being the case it is 

 highly interesting to note a distinct convergence in the quite 



1 Quite recently, however, a species, A. incisivum, preserved at Darmstadt, 

 has been found by Professor Osborn to possess a slight rugosity upon the frontal 

 bones, which probably indicates the presence of a rudimentary horn, and the same 

 author is apparently inclined to place in Aceratherium the horned Teleoceras 

 (see p. 261). 



