420 MR. R. I. POCOCK ON THE EXTERNAL 



JDicJiotomous Classification of the Ursidm, Ailuropoda, Ailurus, 

 and the Procyonidce. 



Although this method of classifying animals has its disadvan- 

 tages on account of its deceptive simplicity and its concealment 

 of cross resemblances, it has the convenience, if not admittedly 

 ai-tificia], of presenting clearly the cbaractei's relied upon by the 

 author and of expressing his views as to the kinship of the 

 groups concerned. 



a. Feet sliort and broad, digits subequal, their pads forming a liglitly 

 curved line in front of the broad plantar pad. Tail reduced to an 

 anal operculum. M. 3 of mandible retained. Carotid foramen 

 situated at posterior end of bulla, close to foramen lacerum 

 posticum. 



a'. Cheek teeth comparatively small, especially jj)«. 1-pm. 3, which 

 are mostly unicuspid and one-rooted, but pm. 1 larger and moie 

 persistent than j)»i. 2; upper _pm. 4 at most tricuspid, its inner 

 root normally fused with the posterior root. Lower pm. 4 short, 

 unicuspid. Zygoma arising approximately above the middle of 

 VI. 2, which is far in advance of the mesopterygoid fossa, the 

 latter preceded by a long edentulous posterior palate. Alisphe- 

 noid canal present. External auditory meatus with its iloor 

 produced to reach approximately to end of thick mastoid process. 

 Mandible not thickened on inner side of coronoid, which does 

 not conceal m. 3 and is comparatively low and but little hooked ; 

 angular well developed, condyle and glenoid surface not abnorm- 

 ally wide. Fore foot without long radio-carpal sesamoid etc.*... UESica:. 



a". Cheek teeth excessively developed, except pm. 1 of upper jaw, 

 which is minute in maxilla, and absent in mandible; jpwj. 2 of 

 maxilla and pm. 2 and pm. 3 of mandible tricuspid; pm. 3 of 

 maxilla sexcuspid : pm. 4 of same, with three large outer and two 

 large inner cusps, its inner root not fused with posterior root ; 

 lower ^Mi. 4 long, tricuspid. Zygoma arising approximately above 

 middle of «?. 1 ; posterior end of m. 2 reached or overlapped by 

 anterior end of mesopterygoid fossa ; no long edentulous pos- 

 terior palate. Alisphenoid canal absent. External auditory 

 meatus with its floor abbreviated and falling far short of 

 long compressed mastoid. Mandible thickened on inner side 

 of coronoid, which conceals m. 3 and is high and hooked ; angular 

 much reduced ; condyle and glenoid surface abnormally wide. 



Fore foot with long radio-carpal sesamoid etc.* AiLUEOPODiD.a;. 



h. Feet comparatively long and slender f, digits unequal, with their pads 

 arranged in a strongly curved line round the comparatively narrow 

 plantar pad. Tail at least long enough to reach the ground. M. 3 

 of mandible suppressed. Carotid foramen on inner side of bulla 

 well in advance oi foramen lacerum postictim. 



b'. Penis short, prepuce close to scrotum. Pads of feet reduced and 

 fuuctionless, completely concealed by woolly hair ; carpal pad 

 remote from plantar pad. Anus in centre of glandular depressed 

 area. Fm. 2 and pm. 3 of maxilla large and three-rooted ; fm. 3 

 quinquecuspid and closely resembling j?ot. 4. Alisphenoid canal 

 present. Forajiien rotnndum minute, lying beneath for. lac. 

 ant., the two separated by a very thin plate of bone and sunk 

 in a common pit ; foramen ovale elongate. Anterior edge of 

 coronoid inclined forwards AiLUEiDiE. 



* For other skeletal characters distinguishing the Ursidse and Ailuropodida?, see 

 the papers by Lankester, Lydekker, and Bardenfleth. 



t It is hardly an exaggeration to say that there is no such thing as a plantigrade 

 carnivore. They all run and walk on the digital and plantar pads, whether they are 

 cats, dogs, bears, or badgers. Bears, when standing on their hind legs, and some- 

 times when walking, place the metatarsal pads on the ground ; but generally these 

 pads, like the carpal pads, are raised from the ground in ordinary progression. A 

 naked metatarsal area does not indicate platigradism, as has been supposed. 



