io6 CHARACTERS OF VERTEBRATE ANIMALS 



striking feature, giving the common name of the animal (Gk. 

 rhinos, of the nose; ktras, a horn), and it is probably responsible 

 for the creation of the legendary unicorn. This defensive structure, 

 when examined microscopically, is seen to be made up of in- 

 numerable horny fibres cemented together, and it has been aptly 

 compared to a big wart, for there is no connection between it 

 and the underlying bone. The African natives have a curious 

 superstition that cups made from this horny material destroy the 

 potency of any poisoned drink which may be poured into them. 



Each one of the four extremities ends in three toes, provided 

 with strong hoofs, there being thus a reduction in the fore-foot 

 as compared with tapirs. The skin is exceedingly thick and but 

 scantily provided with hair, though there is a well-marked tuft 

 on the end of the short tail. The snout is not produced into a 

 proboscis, but the upper lip is extremely flexible. The teeth are 

 well adapted to a vegetable diet, for the grinders have broad 

 crushing crowns of peculiar and characteristic pattern. Upper 

 canines are absent, and sometimes lower ones too. There is 

 much variability in regard to the front teeth, and in the adult 

 these may be absent altogether. 



The group is at the present time confined to South Asia and 

 Tropical Africa, and typical species are the one-horned Indian 

 Rhinoceros (Rhinoceros imicornis), in which the thick skin is 

 disposed in remarkable armour-like folds, and the Common Rhino- 

 ceros (Atelodus bicornis] of Africa, the skin of which is relatively 

 thin and devoid of folds, while there are two well-developed horns 

 placed close together. 



3. Horses and their immediate allies are decidedly the most 

 highly specialized of the odd -toed Ungulates. All the living 

 species belong to the single genus guus, the external characters 

 of which are too well known to need description. It may, however, 

 be noted that the long legs, well suited for swift running, possess 

 but one externally visible toe, corresponding to the middle one of 

 five-toed forms, and provided with a rounded hoof. The front 

 teeth are well developed, and each of them has a deep indentation 

 in the crown, which gets filled up with fragments of the food, 

 and is the cause of the black central area commonly known as the 

 " mark ". The canines are reduced and often absent in the 

 female, but the cheek teeth are numerous, and their flattened 

 crowns exhibit an exceedingly complex pattern. 



