390 DR. ST. G. MIVART ON THE ARCTOIDEA. [Apr. 21, 



ornatus) in the Neotropical. No one species is common to the Old 

 and New Worlds, with the exception of the White Bear {U. niari- 

 timvs). 



The palmar and plantar surfaces are naked save in TJ. maritimus. 

 The ears are erect, rounded, and of moderate size. The eyes are 

 small ; the nose may or may not have a median vertical groove, 

 according to the species. 



There are 14 dorsal, 6 lumbar, 6 sacral, and from 8 to 10 caudal 

 vertebrae. The number of the sacral vertebrae being thus double that 

 of most other Arctoids, the relative length of the sacral region is 

 at its relative as well as absolute maximum, and indeed at its maximum 

 amongst all Carnivora, while the tail is at its relative Arctoid minimum. 

 The length of the limbs relatively is also at the maximum amongst 

 Arctoids after Procyon. The femur is also at its relative maximum 

 amongst all Carnivora. The length of the fourth upper premolar 

 and the breadth of the first true molar are also at their minimum 

 compared with the length of the spine. The scapula has an elongated 

 posterior angle, the femur is relatively slender as well as elongated. 

 The inner condyle of the humerus is not perforated save in TJrsus 

 ornatus '. 



The more significant cranial characters of Ursus have been 

 excellently described and figured by Professor Flower^. In the 

 skulls I have examined I have found the premaxillae and frontals 

 touch, excluding the nasals from the maxillae. The maxilla forms 

 but an exceedingly small floor to the orbit, but it develops a rudi- 

 mentary preorbital process. 



The lateral margins of the basioccipital are each produced into an 

 antero-posteriorly elongated descending process. The paroccipital 

 and mastoid processes are connected by a slight ridge. The mastoid 

 process descends below the meatus auditorius externus. The sagittal 

 f.nd lambdoidal lidges are moderate. The infraorbital foramen is 

 small. The zygomata are well arched out and develop a malar post- 

 orbital process. There are marked postorbital processes to the 

 frontals. The mandible is like that of Ailurus, the coronoid 

 process not ascending much. The angle is long and slender, and 

 extends backwards. There is a distinct subangular process. 



Molar formida=P. j, M. g. 



P. fxSx^ are small, one-rooted, and deciduous, P. ^y:^ are especially 



deciduous. 



Ursus differs from all other Arctoids except Ailuropus in having 

 a third inferior true molar. 



The grinding teeth are, as it were, those of Procyon developed 

 through those of Ailurus in the direction of those of Ailuropus, but 

 their modification is not carried so far as it is in the last-named 

 genus. The fourth upper premolar (the sectorial) has only two 

 external cusps and an internal cinguluin, there being no internal cusp. 



The first upper molar has four cusps, whereof the two outer are 

 much the stronger. 



1 Owen's Anat. of Vertebrates, vol. ii. p. 508. ^ P.Z. S. 1869, p. 7. 



