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Show 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. mari-timus). The palmar and plantar surfaces are naked save in U. 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 Ursus ornatus*. The more significant cranial characters of Ursus have been excellently described and figured by Professor Flower2. 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 rudimentary preorbital process. The lateral margins of the basioccipital are each produced into an antero-posteriorly elongated descending process. The paroccipital and mastoid processes are conuected by a slight ridge. The mastoid process descends below the meatus auditorius externus. The sagittal and lambdoidal ridges are moderate. The infraorbital foramen is small. The zygomata are well arched out and develop a malar postorbital 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 formula = P. {, M . §. P. ^2^3 are small, one-rooted, and deciduous, P. ^ are especially deciduous. Ursus differs from all other xlrctoids 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 cingulum, 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. 2 P. Z. S. 1869, p. 7. |