ORSIDA: 557 
of 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, 
Melursus, and Aflurus. 
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, Urside, Procyonide, 
and Mustelide.+ 
Family Urstp&. 
In existing forms the true molars 4, 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 Atlwropus). 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 4,c4,p4,m4; 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. Vertebre: C 7, D 14, L 6, 8 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. 1885, p. 340. 
2 Linn. Syst. Nat. 12th ed. vol. i. p. 69 (1766). 
