﻿URSUS. 



27 



I cannot detect any constant differences between m. 2 in the two cases, though 

 in some instances there is a tendency for the crown of the tooth to show less 

 posterior contraction in the cave bear than in the others. 



Cave Bear. 

 (3) 111 pm. 4 besides the principal cone 

 there are usually on the inner side two 

 and always one smaller cusp, of which 

 one is anterior in position to the prin- 

 cipal cusp (Busk). Hensel 1 and Owen 

 make similar statements, and Owen 

 also mentions a ridge extending along 

 the outer and back part of the base of 

 the crown as characteristic. Lydekker 2 

 says pm. 4 is relatively short, the inner 

 tubercles are very large and the first is 

 placed more on the inner side than in 

 TJ. arctos. 



Bears of arctos Type. 



Pm. 4 has either only the principal 

 cusp or at most a very small 

 internal tubercle corresponding 

 to the hinder of those met with 

 in TJ. sjpelseus (Busk). 



It is undoubtedly the fact that there is a greater development of accessory 

 tubercles in the case of the tooth in the cave bear than in bears of the arctos type, 

 and this tooth probably affords better characters for the separation of the cave 

 bear than any other part of the skeleton. An examination of a large series of 

 skulls, recent and fossil, of bears of the arctos type, shows that although very often 

 pm. 4 is without any internal cusps or possesses only one small one, and though 

 they never show the development that occurs in TJ. spelseus, yet that in some cases 

 two or even three may be present. Further information with regard to the develop- 

 ment of these cusps is given in the table on p. 31 ; cf. also PL VI, fig. 6. 



Cave Bear. 

 (4) M. 3 is broader in proportion to its 

 length than in bears cf the arctos type. 

 The outer surface is divided into two 

 distinct but low cusps by a deep sulcus. 

 The grinding surface is minutely tuber- 

 culated (Busk) {cf. PI. VI, fig. 5 a). 



Bears of arctos Type. 

 M. 3 is subtriangular and narrower 

 behind than in TJ. spelseus. In 

 typical examples there is no sulcus 

 on the outer border. The grinding 

 surface is coarsely ridged,not tuber- 

 culated(Busk) (cf. PI. VI, fig. 5 6). 



Great stress is laid especially by Busk on the structure of this tooth. It is 

 certainly somewhat broader in proportion to its length in the cave bear than in 

 bears of the arctos type. While no example of m. 3 from a bear of the arctos type 



1 ' Sitzb. Naturf . Freunde Berlin,' 1876, p. 49. 



2 ' Proc. Zool. Soc.,' 1897, pp. 412—426. 



