UNGULATA. 363 



are not united, and the slender lateral digits, nos. n and v, are completely 

 developed. In the hind limb the fibula is reduced so much that only its 

 distal end (the so-called matteolar bone) remains, as in the existing deer ; 

 the hind foot is considerably larger than the fore foot, and the lateral 

 metatarsals, nos. n and v, are reduced to mere splints at the upper end ; 

 metatarsals nos. in and iv remain separate. The elements of the carpus 

 and tarsus exhibit less fusion than in the Tragulidae and true ruminants ; 

 and the keel at the distal end of the metacarpals and metatarsals is 

 incomplete, not reaching to the anterior face of the bone. The typical 

 species is Protoceras celer, known by the nearly complete skeleton from the 

 Lower Miocene (White River Formation) of Dakota. The skull measures 

 0'2 m. in length, and the animal must have been about as large as a sheep. 



In the Lower Miocene of Europe and the Middle or Upper 

 Miocene of North America, undoubted Cervidae or deer also 

 appear for the first time. They agree with the Tragulidae and 

 Protoceratidaj in many respects, but exhibit a distinct advance 

 upon these, not only in the prevailing and characteristic 

 armature of the head, but also in some other features. The 

 facial region of the skull is now slightly bent downwards upon 

 the cranial region, and the tympanic bulhe are hollow. The 

 odontoid process of the axis vertebra is no longer a mere peg, 

 but has become flattened into a half-cylinder. As in Protoceras, 

 the fibula is always so far reduced that only its distal end 

 remains in the small malleolar bone. Some of the carpal and 

 tarsal bones are fused together; and the cannon-bone is in- 

 variably complete on each foot, usually fringed by remains 

 of the lateral digits nos. II and v (fig. 195 c). 



As the various members of the family are traced from the 

 Lower Miocene upwards, they are observed to become gradually 

 specialized in two important respects, namely, in the horns and 

 the teeth. Most of the earlier stages have, indeed, a few 

 surviving representatives; but, taking the family as a whole, 

 the advance is very evident. 



The earliest known genera are hornless, but by the period 

 of the Middle Miocene the males of some forms had acquired a 

 small pair of bifurcated deciduous horns (or antlers) fixed on 

 long bony pedicles of the frontal bones (fig. 207). It is clear that 

 these appendages were shed at times like the antlers of modern 

 deer, because they are marked by the characteristic burr or 



