68 ME. G. BUSK ON THE ANCIENT OR 



well-marked instances be described as bifid. Sometimes, instead of two distinct tubercles, 

 there is a row of several smaller ones ; and it not unfrequently happens that, owing to 

 pressure against the next tooth, the appearance of any tubercles in that situation is 

 destroyed. The inner of the two posterior ridges, after descending a short way, ends 

 in a distinct and sometimes considerable-sized somewhat pointed denticle or accessory 

 cusp, which is that above referred to, and is that noticed by Prof. Owen in speaking 

 of U. jiriscus 1. In a specimen of U.ferox (No. 1137 b, B.M.), although the two divari- 

 cating posterior ridges are quite distinct, there is no appearance whatever of the inner 

 tubercle or cusp ; nor is there any indication of its having been worn off; and the hinder 

 tubercles, if ever present, have been removed by pressure. But in a second specimen 

 of an older animal (No. 1137 a, B.M.), in which the 'tooth is much worn, the site 

 of the internal tubercle is still quite visible, as weU as the presence of the bifid pos- 

 terior talon ; and in a specimen, also a good deal worn, of the same species in the 

 College of Surgeons, the same appearances are distinctly shown. In the typical speci- 

 men of U. prisons (fossilis) in the British Museum, whose teeth are also much worn, the 

 inner tubercle is very faintly indicated, nor is the bifid talon distinctly discernible. In 

 general characters, therefore, the tooth exactly resembles that of U.ferox (No. 1137 b, 

 B.M.}. 



In U. arctos the pm. 4 is distinguished, besides its usually much smaller dimensions, 

 by the extremely minute size or total absence of the inner tubercle, which in this 

 species, so far as I have seen, rarely exceeds a large pin's head in size, and is often 

 wholly wanting. The posterior talon sometimes exhibits a very minute tubercle, but is 

 more usually quite smooth, and never distinctly bifid as in U. ferox. 



On applying these observations on the teeth to the diagnosis of the Gibraltar Bear, it 

 appears to me that that form occupies a position intermediate, as it were, between 

 JJ. arctos and U.ferox. 



1. As regards the second upper molar. In the Gibraltar jaw this tooth resembles 

 that of U. ferox, besides its size, in its comparatively slight attenuation behind, and 

 that of U. arctos in the apparent falling inwards of the side, though to what extent 

 this reached cannot be determined in the present worn condition of the tooth. 



2. The third lower molar also resembles that of U.ferox much more nearly than 

 that of U. arctos in its greater dimensions and more oblong form, corresponding with 

 the larger and longer upper molar ; but there is no appearance whatever of a sulcus in 

 the outer border, such as would most probably have been seen in a tooth of the same 

 size in U. fossilis or U.ferox. 



3. The fourth lower premolar, on the other hand, in its comparatively small dimen- 

 sions, the diminutive size of the inner denticle, which is not bigger than a pin's head, 

 and the perfectly simple nou-tuberculated inner border, more nearly resembles, in 

 fact quite agrees with, the same tooth in U. arctos. 



' Brit. Foss. Mammals, p. 81. 



