CAMELIDjE 295 



unlike those of Dichodon; but the navicular and cuboid bones of 



the tarsus were fused together, and the metatarsals had united to 

 form a "cannon-bone," although the metacarpals still remained 

 distinct. It is not improbable that upper incisors were wanting ; 

 and it has been suggested that we have in this genus the ancestral 



type of the Tragrdidos and Cervidce. 



Tylopoda. 

 Family Camelid.e. 



This group is represented at the present day by the two species 

 of Camels of the Old World and the Llamas of South America, 

 collectively constituting the family Camelidce. The special characters 

 which the Llamas and Camels have in common, and the combina- 

 tion of which distinguishes them from the rest of the Artiodactyles, 

 are as follows. The premaxilla? have the full number of incisor 

 teeth in the young state, and the outermost is persistent through 

 life as an isolated laniariform tooth. The canines are present in 

 both jaws, and those of the mandible are differentiated from the 

 long, procumbent, and spatulate incisors, being suberectand pointed. 

 The crowns of the true molars belong to the crescentic or selen- 

 odont type, and are very hypsodont ; but one or more of the 

 anterior premolars is usually detached from the series, and is 

 of simple pointed form. The auditory bulla is filled with cancellous 

 tissue. The hinder part of the body is much contracted, and the 

 femur long and vertically placed, so that the knee-joint is lower 

 in position, and the thigh altogether more detached from the 

 abdomen than in most quadrupedal mammals. The limbs are 

 long, but with only the third and fourth digits developed ; no 

 traces of any of the others being present. The trapezoid and mag- 

 num of the carpus, and the cuboid and navicular of the tarsus are 

 distinct. The two metapodial bones of each limb are confluent for 

 the greater part of their length, though separated for a considerable 

 distance at the lower end. Their distal articular surfaces, instead 

 of being pulley-like, with deep ridges and grooves, as in other recent 

 Artiodactyles, are simple, rounded, and smooth. The proximal 

 phalanges are expanded at their distal ends, and the wide, depressed 

 middle phalanges are embedded in a broad cutaneous pad, forming 

 the sole of the foot, on which the animal rests in walking, instead 

 of on the hoofs. The ungual phalanges are very small and nodular, 

 not flattened on their inner or opposed surfaces, and not completely 

 encased in hoofs, but bearing nails on their upper surface only. 

 The cervical region is long and flexuous, and the vertebrae of which 

 it is composed are remarkable for the position of the canal for 



