URSUS ARCTOS. 79 
On a closer comparison, especially of the dental system, 
differences appear which are not explicable on the known 
influence of external circumstances operating during a 
lengthened period of time. 
The upper jaw of the Fen Bear differs from a similar 
sized one of the great Cave Bear in the much shorter inter- 
space between the canine tooth and the third molar tooth 
counting from behind forwards ; it differs hkewise in haying 
this interspace occupied by two small and simple-fanged pre- 
molars, completed in outline in fig. 24. The crown of 
the penultimate grinder is broader in proportion to its 
length or antero-posterior diameter. The difference in 
regard to the presence of the two first false molars must be 
allowed due weight, since the present Fen Bear has its 
grinders much worn, whilst the Cave Bear, with which it is 
compared, is a younger but full-grown specimen, with the 
tubercles of the grinding teeth entire, and the last molar 
tooth of the Fen Bear has a narrower posterior termination 
than in the Cave Bear. The Fen Bear differs also from 
the Ursus priscus, a smaller extinct species of Cave-haunt- 
ing Bear, which retains the two first false molars, by their 
being in contact, which results from the narrower interspace 
between the canine and the third false molar, which inter- 
space is relatively as wide in the Ursus priscus as in the 
Ursus speleus, and a great proportion of this interspace 
divides the first from the second false molar in the Ursus 
priscus. This likewise cannot be a difference dependent 
on age or sex, for the jaw of the Fen Bear here described 
belonged to an individual absolutely larger than the Ursus 
priscus, with which it was compared ; and, judging from the 
size of the canine teeth, the present specimen of the Fen Bear 
was probably an old male. The grinding surface of the 
molars prove it to have been also an older individual than 
