74 CAUDAL VERTEBRAE. [CHAP 



to 20), in the Oxen and in some Antelopes (Koodoo), and 

 least so in some Deer, especially Moschus, in which animal 

 the tail is quite rudimentary. 



The Elephant has a long tail, composed of 31 vertebras 

 of simple character, without chevron bones. 



In the Hyrax the tail is short, consisting of about 4 to 9 

 vertebrae. 



As the tail is the principal organ of locomotion in the 

 CETACEA, it is always very well developed, and consists of 

 numerous (from 18 to 30) vertebrae. 



Chevron bones are always present, and of simple character, 

 though with long compressed median spines (see Fig. 29, 

 p. 71). They are mainly attached to the posterior extremity 

 of the vertebra immediately in front of them. 



The characters of the caudal vertebra in the various 

 animals of the order are tolerably uniform, the tail having 

 the same function in all. In the anterior part of the region 

 the bodies are very massive and cylindrical ; the arches have 

 high spines, with metapophyses on their anterior edges, and 

 the transverse processes are tolerably long, and directed 

 straight outwards. In passing backwards the arches and all 

 the processes gradually disappear, and the bodies become 

 much compressed, and elevated vertically. Suddenly a 

 change takes place (at the spot where the end of the 

 vertebral column becomes enclosed in the horizontal, 

 laterally extended cutaneous expansions, constituting the 

 " flukes " of the tail,) and the vertebrae altogether alter 

 their characters, becoming much smaller, wide transversely 

 and depressed. There is always one vertebra which is 

 transitional in its character between these two forms. Most 

 of the caudal vertebras are perforated by a vertical canal on 

 each side, either passing through the base of the transverse 

 process, or in the posterior vertebrae through the body of 



