URSUS. 



29 



(6) The convex character of the lower jaw (Owen and Falconer).— Neither of the 

 characters 5 or 6 seems to be constant. 



(7) The relative shortness of the limb bones, especially of I In- tibia in the cave 

 bear (Gaudry and Boule). — This appears to be a constant character. 



(S) Tl/r relative weakness <>/ the hind limbs (Gaudry ami Boule). — Gaudry 

 and I Joule's suggestion in tins connection has been referred to on p. 22. 



(9) The relative narrowness of the femur in proportion i<> its length, the small 

 she of tin: tuberosity <ihoc<> the internal condyle, mid the projection of the lesser tro- 

 chanter it little beyond the inner margin in the cave hear (Owen). 



Comparison of the various Bears of the arctos Type. 



With regard to the distinction between the brown and grizzly bears, there is by 

 no means such a consensus of opinion as there is concerning the distinction of 

 the cave bear. Not only de Blainville (1844), but Middendorff (1851), Midler 

 (1872), Busk (1873), Boyd Dawkins (1877), Lydekker (1881 and 1885), and 

 Brown (1894), doubt whether the brown and grizzly bears can be separated 

 from one another. 



The points of difference, whether valid or otherwise, have been noted as follows, 

 and are mainly due to Owen and Busk. 1 



U. arctos. 

 1. in. 2, The unworn crown is much compressed ; 

 there are only two cusps on the outer border 

 of the tooth, of which the anterior is con- 

 siderably the larger, and the posterior has in 

 most cases a small portion in front con- 

 stricted off so as to form an accessory 

 tubercle between the two cusps (Busk). 



U. horribilis. 

 The unworn crown is less compressed, and there 

 are occasionally three outer cusps ; the anterior 

 two are more nearly equal in size than U. arctos, 

 and the third is always small and often wanting. 

 There is no accessory tubercle cut off from the 

 anterior border of the posterior cusp (Busk). 



2. pin. 4 tends to be relatively long. pm. 4 tends to be relatively shorter, and there is 



more of a shelf-like projection of the cingulum 

 at the antero-internal corner (Brown). 2 



3. There is a relatively narrow space between c. There is a relatively wide space between c. and 



and i)in. 4. pin. 4. 



4. The inner posterior cusp or tubercle of pm. 4 

 is very small or absent, and if present there is 

 no bifid posterior talon projecting from it 

 (Busk). 



The inner posterior cusp of pm. 4 is better deve- 

 loped than in U. arctos, and the posterior talon 

 is commonly bifid or marked by two longi- 

 tudinal ridges running back from it to the end 

 of the tooth (Busk). 



l -Trans. Zool. Sue.,' x, 1877, p. GO. 



- • Proc. Acad. Nat. Sci. Philad.,' 1894, p. 119. 



