﻿10 PLEISTOCENE MAMMALIA. 



III. DESCRIPTION OF THE REMAINS. 



It may be well to begin with a statement of the distinctive osteological 

 characters of bears. They agree with the other Arctoiclea in the following respects l : 

 (1) there are five well-developed digits; (2) the auditory bulla is simple with no 

 trace of a dividing septum, and the inferior lip of the auditory meatus is considerably 

 prolonged ; (o) the paroccipital process of the exoccipital is more or less triangular 

 and is directed backwards, outwards, and downwards, standing quite apart from 

 the bulla; (4) the mastoid process of the periotic is widely separated from the 

 paroccipital and generally very prominent ; (5) the carotid foramen is large and 

 placed on the inner margin of the bulla, usually near the middle, but occasionally 

 more posteriorly ; (6) the condyloid foramen is distinct and exposed and never sunk 

 into a common opening with the foramen lacerum posterius ; (7) the glenoid 

 foramen is always present and usually conspicuous ; (8) a large penial bone occurs. 



The family Ursidas is characterised by the following features: 3 In existing 

 forms the true molars are § and have broad flat tuberculated crowns. The three 

 anterior premolars of both jaws are rudimentary and often deciduous. The fourth 

 upper premolar, the carnassial tooth, has no third or inner root. An alisphenoid 

 canal is present. The auditory bulla is depressed and scarcely at all inflated. 

 The feet are plantigrade. There is no entepicondylar foramen to the humerus. 



As noted by de Blainville, a bear's skeleton presents certain resemblances to 

 that of man, dependent partly on the animal's habit of sitting on the ischia, 

 partly on the plantigrade method of walking. 



a. The Skull (Plates I— V). 



(1) Distinctive Features of the Skull in the Genus Ursus. — The skull is more or less 

 elongated. The orbits are small and the post-orbital bar is incomplete. The palate 

 is prolonged considerably behind the last molar tooth. An alisphenoid canal is 

 present. The pterygoid has a well-developed hamular process. 



The following are the features in the skulls and teeth of bears, in which the 

 greatest amount of variation takes place, and to which special attention should be 

 paid in attempting to discriminate between the different species : 



(1) The presence or absence of the anterior premolars ; 



(2) The length of the interspace between c. and pm. 4, and between c. and 

 pm. 4 ; 



(3) The form of pm. 4 and m. 3; 



(4) The width of the posterior narial opening ; 



(5) The shape of the jugal arcade ; 



1 Flower and Lydekker, ' Mammals Living and Extinct,' p. 586. 



2 Ibid., p. 556. 



