318 ORDER PACHYDERM ATA. FAMILY ELEPHANTIDJ2. 



ant marks of resemblance, are here so various, as to require a 

 separate description for each family ; it can only be stated 

 regarding the former, that they are chiefly formed for a vegetable 

 diet (though some species are omnivorous) ; whilst the extremi- 

 ties are constructed for support only, the clavicles being absent, 

 the bones of the fore-arm consolidated, so that the power of 

 rotation is altogether lost, and the toes included in a callous 

 skin, or in proper hoofs. The order may be subdivided into four 

 sections; distinguished by the following characters: 1. The 

 PROBOSCIDEA, possessing a prolonged snout or proboscis, and 

 having five toes on each foot, included in a very firm horny skin. 

 2. The PACHYDERMATA ORDINARIA, in which the feet have four, 

 three, or two toes on each foot. 3. The SOLIDUNGULA, in which 

 the foot has but one apparent toe. 4. The CETACEA HERBIVORA, 

 in which the posterior extremities are wanting, and the anterior 

 formed as paddles for swimming. 



286. The Proboscidean group contains but one family, the 

 ELEPHANTID.E, or Elephant tribe ; and this at present consists of 

 but a single genus. The Elephants, of which only two species 

 the Asiatic and the African at present exist, are distinguished, 

 not only by their proboscis, but by the absence of front teeth in 

 the lower jaw, and by the possession of two enormous tusks, 

 which project downwards from the upper. These, like the long 

 canines of the Rodentia, grow from a pulp which is continually 

 forming new ivory (ANIM. PHYSIOL., 177) ; and may be 

 regarded as closely analogous to the teeth, which are character- 

 istic of that order. The analogies between the largest and the 

 smallest of the terrestrial Mammalia do not,however, stop here. 

 They may be traced, also, in the structure of the molar teeth, 

 which are formed of alternating vertical plates of enamel, bone, 

 and crusta petrosa, arranged transversely to the jaw, as in the 

 Rodentia ( 216). These grinders succeed one another, from 

 behind forwards, each tooth, as it is worn, giving way to 

 another, which is pushed into its place ; so that the Elephant 

 may have one, or two, of these large grinders on each side, 

 according to the period of their development. The molars are 

 said to be thus changed eight times ; the first tusks of the young 



