URSIDjE 



557 



i>f the bulla, usually near the middle, but occasionally more 

 posteriorly; the condyloid foramen is distinct and exposed, and 

 never sunk into a common opening with the foramen lacerum 

 posticum ; and the glenoid foramen is always present, and usually 

 conspicuous. The alisphenoid canal is absent except in Ursus, 

 Mdwrsus, and JElurus. 



It has been already observed (p. 501) that the evidence of fossil 

 forms, so far as it goes, is not in favour of the Arctoidea being a 

 natural group ; so that its retention must be regarded as a some- 

 what provisional measure, largely based on its convenience. The 

 group may be divided into the three families, Ursidce, Procyonidce, 

 and Mustelidcv. 1 



Family Ursidce. 



In existing forms the true molars f , with broad, flat tuber- 

 culated crowns. Typically the three anterior premolars of both 

 jaws rudimentary and often deciduous. Fourth upper premolar 

 (carnassial) with no third or inner root. An alisphenoid canal 

 (except in JEluropus). Skull with the auditory bulla depressed, and 

 scarcely at all inflated. Feet plantigrade. No entepicondylar 

 foramen to the humerus. Kidneys conglomerate. Geographical 

 distribution extensive. 



Ursus. 2 — Dentition : i %, c \, p ^, m % ; total 42. The three 

 anterior premolars above and below one-rooted, rudimentary, and 

 frequently wanting. Usually the first (placed close to the canine) 

 is present, and after a considerable interval the third, which is 

 situated close to the other teeth of the molar series. The second 

 is very rarely present in the adult state. The fourth (upper car- 

 nassial) differs essentially from the corresponding tooth of other 

 Carnivores in wanting the inner tubercle supported by a distinct root. 

 Its sectorial characters are very slightly marked, and it is much 

 smaller than the first molar. The crowns of both the true molars 

 are longer than broad, with flattened, tuberculated, grinding surfaces. 

 The second has a large backward prolongation or heel. The lower 

 carnassial has a small and indistinct blade and greatly developed 

 tubercular heel. The second molar is of about the same length, 

 but with a broader and more flattened tubercular crown. The 

 third is smaller. The milk-teeth are comparatively small, and shed 

 at an early age. Skull more or less elongated. Orbits small and 

 incomplete behind. Palate prolonged considerably behind the last 

 molar tooth. Vertebrae: C 7, D 14, L 6, S 5, C 8-10. Body 

 heavy. Feet broad, completely plantigrade ; the five toes on each 

 foot all well developed, and armed with long compressed and 



1 For full details of the Arctoidea see Mivart, Proc. Zool. Soc. 18S5, p. 340. 

 2 Linn. Syst. Nat. 12th ed. vol. i. p. 69 (1766). 



