URSUS SPELXUs. 107 
middle, or miocene tertiary formations, through the older 
and newer pliocene, and that the genus surviving, or under 
a new specific form reappearing after the epoch of the depo- 
sition and dispersion of those enormous, unstratified, super- 
ficial accumulations of marine and freshwater shingle and 
gravel, called drift and diluvium, has been continued 
during the formation of vast fens and turbaries upon the 
present surface of the island, and until the multiplication 
and advancement of the human race introduced a new cause 
of extermination, under the powerful influence of which 
the Bear was finally swept away from the indigenous 
Fauna of Great Britain. 
The adjoining figures illustrate the characters derivable 
from the lower jaw and its dentition, of three of the species 
by which the genus has been represented in England, 
during the different periods above cited, c, fig. 35, is the 
Jaw of the extinct Ursus speleus, from the Norfolk pliocene ; 
it shows the complex premolar (3 p) and the long toothless 
interval between it and the canine: B is the Jaw of the 
Ursus priscus of the post-pliocene epoch, in which the inter- 
val is shorter and retains the first small premolar (1 p): a 
is the jaw of the Ursus Arctos from the Cambridge fen, 
in which the shorter interval retains two small premolars, 
and the third (3 p) has a more simple crown. 
With the present experience of physiologists as to the 
range of variety of which a specific form is susceptible, 
through the long continued operation of external influences, 
we cannot attribute the anatomical differences which have 
been pointed out in the fossil teeth and bones of Bears derived 
from the above-cited series of formations, to varieties of one 
species produced by such accidental causes. On the con- 
trary, those Bears which existed anterior to the present con- 
dition of the surface of the British Islands must be referred 
to two species distinct from any now known, and which have 
