THE ROCK-BADGER OR CONY FAMILY. 



39 



is completed on all the four feet of the rhin- 

 oceroses and on the* hind-feet of the Hyracida 

 and tapirs, so that these feet are composed 

 only of the dominant middle toe together with 

 the second and fourth digits. The gradual 

 loss of the latter two digits can be traced in 

 the series of fossil horses. In the fossil genus 

 Hipparion they no longer touch the ground, 

 and carry so-called false hoofs, and in our 

 present-day horses they are reduced to two 

 little style-like splint-bones, as they are called, 

 attached to the two sides of the enormously 

 enlarged metacarpal (or metatarsal) bone. 

 This reduction, which converts the limb into 

 a column, leads, as may easily be imagined, 

 to the loss of the ulna in the fore-limb and to 

 that of the fibula in the hind-leg, so that 

 the lower arm and lower leg, each originally 

 composed of two distinct bones, come at last 

 to consist only of the radius (chief bone of the 

 fore-arm) and tibia (shin-bone) respectively. 



The limbs themselves are sometimes 

 shorter and more massive, as in the rhino- 

 ceroses and the tapirs, sometimes longer, as 

 in the horses; but whatever their special 

 organization may be, one characteristic is 

 always present: the thigh-bone always has 

 below the great trochanter a separate bony 

 process, known as the third trochanter, for 

 the attachment of the muscles. This process 

 often becomes remarkably large, as in the 

 rhinoceros, and since it is never absent it 

 affords an excellent distinguishing character. 



What still further distinguishes the Peris- 

 sodactyla is the large number of vertebrae 

 between the neck and the pelvis— of rib- 

 bearing dorsal vertebrae and of lumbar 

 vertebrae. The number of these vertebrae is 

 never less than 22, it may rise even to 29 or 

 30. In a rock-badger belonging to the Cape 

 I have counted as many as 21 rib-bearing 

 and 8 lumbar vertebrae. 



The dentition presents highly archaic 

 characters in the cheek-teeth along with 

 pretty considerable modifications in the front 

 teeth. We always find, in fact, in the first 



instance seven cheek-teeth in each half of the 

 jaw, both above and below, and these re- 

 semble each other so closely that it is scarcely 

 possible to distinguish premolars from true 

 molars by the form. All these teeth are 

 compound and exhibit on the grinding surface 

 of the crown varied forms of enamel folds, 

 which become more and more prominent as 

 the teeth get worn away by use, and which, 

 at least in the horse series, increase in com- 

 plexity from ancient to more recent times. 

 The close-set series of cheek-teeth are separ- 

 ated from the front teeth by a larger or 

 smaller interval or diastema. In this front 

 set of teeth there prevails great diversity. 

 The incisors, originally present in considerable 

 number, may become specialized as in the 

 Hyracida, or become deciduous as in the 

 rhinoceroses; the canines, always weak, may 

 become quite rudimentary. 



The brain of all perissodactyles is not very 

 large, and the hemispheres of the cerebrum 

 always leave the cerebellum uncovered. The 

 brain of the rock-badger shows some very 

 simple convolutions; the hemispheres of the 

 large genera, as is always the case with larger 

 animals, have more complex convolutions. 

 The intelligence of these animals, even of the 

 most perfect, such as the horse, is always 

 very limited. The stomach is simple and 

 relatively small, and shows no tendency to 

 a further subdivision. The intestines, and 

 especially the caecum, are very long, as in 

 many entirely herbivorous animals. 



THE 

 ROCK-BADGER OR CONY FAMILY 



(HYRACIDA). 



This family contains animals of the size of 

 a rabbit, which are so very different from the 

 other Perissodactyla in respect of various 

 characters that they may very well be taken 

 to form a sub-order. 1 Formerly these little 



1 By many naturalists they are regarded as constituting a separate 

 order. — Tr. 



