URSUS. 27 



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

 in sonic 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. ■ Bears of arctos Type. 



(8) In pin. -1. besides the principal cone Pm. 4 has either only the principal 

 there are usually on the inner side two cusp or at most a very small 



and always one smaller cusp, of which internal tubercle corresponding 



one is anterior in position to the prin- to the hinder of those met with 



cipal cusp (Busk). Hensel 1 and Owen in U. spelams (Busk). 



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 

 U. arctos. 



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 onby one small one, and though 

 they never show the development that occurs in II. 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. 0. 



Cave Bear. Bears of arctos Type. 



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



length than in bears of the a reins type. behind than in U. spelssiis. In 



The outer surface is divided into two typical examples there is no sulcus 



distinct but low cusps by a deep sulcus. on the outer border.. The grinding 



The grinding surface is minutely tuber- surface is coarsely ridged,nottuber- 



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



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 in. 3 from a bear of the arctos type 



1 'Sitzb. Naturf. Freunde Berlin.' 1S7C, p. 49. 

 - • Proc. Zool. Soc.,' L897, pp. 412 126. 



