REPORT OX TI-IE EXPLORATION OF BRIXHAM CAA 7 E. 
539 
three, are almost invariably found. When two exist, as is commonly the case in U. circtos, 
they are almost always the first and third, one being situated close to the canine and the 
other immediately in front of the pm 4. But in two of the jaws in the Brixham Col- 
lection the two sockets are placed close together immediately behind the canine, leading 
to the supposition that in these cases it was the third and not the second premolar which 
was suppressed. There is, however, another character belonging to the lower jaw (which 
was, I believe, originally pointed out by Mr. Watekiiouse) which appears to be of some 
value ; this is the comparative thickness of the articular condyle. In all collections of 
fossil ursine mandibles they may manifestly be divided into two groups, from the differ- 
ence in the proportions of this part ; and as the difference in question is also accom- 
panied, in the majority of instances, by certain differences in the teeth distinctive of 
U. spelceus and U prisons, it may be taken as an additional specific character. The same 
difference, even to a still greater extent, is found between the mandibular condyle in the 
Lion and Tiger — the former having it very much thicker than the latter, even when the 
jaw itself and the teeth are of the same size. The thick condyle characterizes the lower 
jaw of U. spelceus. 
As regards the other bones of the skeleton, I am not at present in a position to say 
any thing in detail. Many of them undoubtedly present differences which must be 
regarded as specific ; but I am not aware that these distinctions have yet been assigned 
to the respective species. Amongst other bones in the Brixham Collection, differences 
will be observed in the humerus, more especially as regards the angle at which the 
supinator ridge descends from the shaft. Certain differences also may be noticed be- 
tween two tolerably perfect unciform bones which are figured in Plate XLVI. figs. 9 & 10, 
and in the case of two astragali (one of which, however, is unfortunately very imperfect) 
which are represented in figs. 7 & 8. 
But it is upon the teeth that we must chiefly rely in the distinction of species in fossil 
Bears, affording as they do the best and most easily appreciated characters. The cha- 
racters of the teeth are derived partly from their relative and absolute dimensions, and 
in some of them more especially from their form. As regards the dimensions of the 
teeth, it is necessary to consider them not so much individually as relatively to each 
other in the same jaw. On this account the Brixham Collection, though rich in 
separate teeth, does not afford very abundant materials for their proper comparison 
inter se. I have placed in the following Table the dimensions of the various teeth 
occurring in the collection which are sufficiently entire for the purpose, which will give 
all the requisite information on that point, and will proceed to say a few words with 
respect to the forms of some among them which present the most marked characters. 
