X HORNLESS EXTINCT FORMS 259 



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

 in the lower jaw. This Acerathcriicw 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 JRh. tichorhimis, which possessed a woolly covering and had 

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

 horned. 



The post-Pli(.)cene and European ElasmofJicrium was a colossal 

 rhinocerotine creature. Tliis great beast had two horns and a 

 body 15 feet long. Its liml)s 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 Osliorn is inclined 

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

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

 those of a Horse in l)eing hypselodont and prismatic in form. As 

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

 typical Rhinoceroses ; there was an enormous horn posteriorly, 

 supported on a huge boss of l;»one, 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 Rhinoceroses l)elonging to 

 the restricted genus lihinoceros 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 Rhinoceroses of America were mostly hornless. Diccra- 

 thcrium 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 Rhinoceroses. Accratlicrium of 

 both divisions of the globe prol)aJ)ly 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 



^ Quite recently, however, a species, A. incisivum, preserved at Darnihtadt, 

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

 bones, which j)robably indicates the presence of a rudimentary horn, and the same 

 author is apjiarently inclined to place in Aceratherium the horned Telcocerns 

 (see p. 261). 



