298 MAMMALIA. 



. n , mi j . i f . i. 0, c. 1. pm. 3, m. 3 



inflected. The dental formula is - . No traces 



i. 3, c. 1, pm. 3 or 4, m. 3 



of incisors have been observed in the premaxillae, even of the most 

 immature specimens, though a series of shallow depressions are sometimes 

 seen on the oral margin of these bones. The lower incisors, however, are 

 always well-developed, each with a single closed root in its own separate 

 socket, and with the crown completely invested in enamel. The upper 

 canines are enormously developed, but relatively larger in some indi- 

 viduals (presumably males) than in others (presumably females). The 

 crown forms a trenchant tusk, enamelled but not serrated ; while the root 

 is deeply implanted in the maxilla, closed in the adult, and sometimes 

 extending even into the base of the maxillary horn-core. The lower 

 canine is small, resembling the incisors with which it is in continuous 

 series ; while there is always a diastema between this tooth and the hinder 

 teeth in both jaws. All the premolars and molars of the upper jaw are 

 implanted by three roots, while those of the lower jaw exhibit only two 

 roots. The crown is always remarkably low (brachyodont), while the 

 transverse ridges become almost obliterated by wear. The milk-dentition 

 is scarcely known, though there are indications that all the incisors, 

 canines, and premolars had deciduous predecessors. The cervical ver- 

 tebrae are as usual seven in number, and much resemble those of the 

 elephants, though altogether about one-third longer and thus rendering a 

 proboscis unnecessary. The trunk vertebrae are about twenty-three in 

 number, with the centra relatively longer than those of the cervicals, and 

 with thin epiphyses which are often imperfectly ossified. About nineteen 

 bear free ribs, while at least four are lumbar. The series of sternal bones 

 is not completely known. The sacmm comprises four vertebrae, and the tail 

 seems to have been very slender. All the limb-bones are nearly or quite 

 solid. There is no clavicle. The fore limb is shorter than the hind limb 

 and considerably bent at the elbow joint, so that the muscular attach- 

 ments on the robust humerus are very prominent. The radius and ulna 'I 

 are almost equal in stoutness, and the latter rises into a large olecranon 

 process. The fore foot is shown in fig. 169 B. The central bone of the 

 carpus may be separate in very young animals, but it is not observable in 

 the adult. The hind limb when at rest forms an almost vertical column. 

 The pelvic bones are fused together, first into two independent ossa 

 innominata, then into a single mass, but always articulating in an open 

 suture with the sacrum. The ilium is much expanded and rounded in 

 outline. The femur exhibits no trace of a third trochanter, and is much 

 longer than the tibia, which bears a very prominent tuberosity for the 

 attachment of the patellar ligament. The fibula is comparatively slender, 

 but thickest at its lower end. The hind foot, which is smaller than the 

 fore foot, is shown in fig. 169 c. The typical species, Dinoceras mirabile 

 (fig. 169), is almost completely known from more or less fragmentary 

 skeletons discovered in the Bridger Eocene of Wyoming, and seerns to 



