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 likewise in having 

 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 speleeus, 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 



