2 LLOYDS NATURAL HISTORY. 



lower portions of the limbs have not undergone such excessive 

 elongation, while the fore-feet retain the original typical number 

 of five toes, and in the hind pair the number of digits is only 

 reduced by one. Then, again, whereas in the Antelopes the 

 movements of the fore-limb have become restricted to a 

 backwards-and-forwards direction, while its extremities (like 

 those of the hind-limb) are encased in solid horny hoofs, in 

 the Cats the same limb is capable of a free rotatory motion, 

 and its toes are armed with sharp and powerful claws. These 

 divergencies of structure are, of course, to be accounted for by 

 the respective exigencies of the mode of life of the members 

 of the two groups ; the Antelopes having merely had to attain 

 a speed sufficient to enable them to escape the attacks of their 

 enemies, while the Cats had not only to equal or surpass this 

 speed, but to have the power of striking down their prey and 

 holding it when struck. 



Another parallelism between the two groups may be detected 

 in their dentition, which in each case has been specially modi- 

 fied for the exigencies of a particular mode of existence, and 

 has thus departed very widely from the generalised type pre- 

 valent in many of the older Mammals, and which is partially 

 retained in the common Pig. In the Antelopes the object of 

 the modification has been to produce a type of dentition best 

 suited for the cropping and mastication of grasses. Conse- 

 quently, while the teeth of the cheek-series, that is to say, the 

 pre-molars and molars, have been retained in their full number, 

 though their crowns have been lengthened, and likewise compli- 

 cated by infoldings and flutings of their summits and sides, so 

 as to form the best possible masticating apparatus, the tusks, 

 or canines, have disappeared, either totally or as such, while 

 the lower incisor teeth have assumed spatulate crowns admir- 

 ably adapted for plucking off the tufts of grass seized in the 

 tongue, by biting against the hard, callous pad in the front of the 



