544 
REPORT ON THE EXPLORATION OF BRIXHAM CAYE. 
exist between TJ. spelaeus and TJ. prisons ; but unfortunately the teeth are wanting in 
both. Again, upon taking the measurements of the teeth in the fossil ursine remains 
from Grays, I find that the mean dimensions of those in three mandibles agree very 
closely with the sizes in TJ. prisons and TJ. ferox , as will be seen in the subjoined 
Table III., in which, for convenience, I have brought together only the mean dimensions 
of the molar teeth, adding those of the specimens from Grays. 
Table III. — Mean Dimensions of Molar Teeth in Fossil and some recent Species. (0"*01.) 
pm 4. 
m 1 . 
m 2. 
pm 4. 
m 1. 
m 2. 
m 3. 
ms. 
ms. 
U. spelaus 80x60 
112x80 
180x91 
64x43 
114x58 
116x74 
118x84 
372 
412 
TJ. priscus ? 63 X 52 
90x71 
147x79 
57x31 
100x52 
105 X 64 
86x67 
300 
348 
U. ferox , 62x47 
91x67 
150x73 
51x30 
97x46 
102x63 
92x62 
303 
342 
TJ. arctos 61x43 
83x61 
126x66 
45x28 
90x42 
90x55 
70x54 
270 
295 
TJ. maritimus 63 X 37 
70x60 
108x60 
53x28 
86x38 
81x45 
61x47 
241 
.281 
Ursus (Brixham) I 67 X 55 
94x64 
150x77 
54x31 
105x53 
108x67 
91x68 
312 
358 
Ursus (Grays) 
100x72 
150x75 
58x37 
101x54 
100x69 
87x70 
346 
In these cases, again, we find a coincidence, as it seems to me, too close to be acci- 
dental ; and I think further inquiry will demonstrate beyond doubt that the TJ. prisons 
is the same species as those above noticed from Ireland and Grays. 
As regards the other species of Bear included in Table II., it is scarcely necessary 
here to make any remark. The numbers themselves will show pretty conclusively that, 
with the exception perhaps of TJ. arctos, none can be well confounded with either TJ. 
spelaeus or TJ. prisons. In isolated teeth it will in many cases be quite impossible to 
distinguish between the smaller forms of TJ. prisons or TJ. ferox and the larger ones of 
TJ. arctos , in which species, as will be observed, the maximum size of the teeth equals, 
and in some instances exceeds, the minimum size of the same tooth in the others ; whilst 
in many of the teeth there is very little, if any, difference of size at all. The most charac- 
teristic teeth with respect to size, as distinctive between TJ. prisons ( fossilis , Gldf.) and 
TJ. arctos , appear to be m 2, m 2, and m 3 ; but even in these cases the maximum size in 
TJ. arctos sometimes equals the minimum in the other. This circumstance is an 
exemplification, in addition to others which might be adduced, of the great tendency to 
variation exhibited in TJ. arctos, as has been already noticed. Its existence, however, 
shows the necessity in many cases of caution in the determination of a doubtful species 
from isolated teeth. Though I believe the mean dimensions, taken from a sufficient 
number of teeth in situ, may to a certainty be relied upon, mistakes may otherwise 
readily arise. 
Having thus seen reason from the dimensions alone to refer TJ. prisons ( fossilis , Gldf.) 
to TJ. ferox, and to believe that the greater part of the Brixham specimens belong to the 
