762 



Comparative Morphology of Chordates 



the pes three. All of the digits except the first of the three on the pes 

 terminate in broad, blunt, horny structures resembling nails or tiny 

 hoofs rather than claws. The exceptional toe bears a long curved claw. 

 Although the feet are plantigrade, their blunt horny structures appear 

 ungulate in nature. The animals are herbivorous and the stomach is 

 divided into two compartments. The gallbladder is lacking. 



Two Genera of these animals are usually recognized, Hyrax (Pro- 

 cavia: Fig. 576) and Dendrohyrax. The name "cony" is commonly 







B!^iil 



^ 



^ 





Fig. 576. Hyrax capensis. (Courtesy, Flower and 

 Lydekker: "Introduction to the Study of Mammals," 

 London, A. & C. Black, Ltd.) 



applied to them, but unfortunately the European rabbit also is often 

 called by that name. They are found only in western Asia and northern 

 Africa. Hyrax is terrestrial in habit but Dendrohyrax is said to live in 

 hollows of trees. 



Order 17: SIRENIA. Aquatic, but less highly adapted to aquatic 

 life than whales — body relatively short and thick: head more distinct 

 from body than in whales: no median fin; horizontal caudal fin. Pec- 

 toral limb externally finlike as in whales: pelvic limb represented only 

 by small vestiges embedded in body-wall. 



Dentition heterodont; incisors lacking or, at most, one pair of 

 tusklike uppers; no canines; cheek-teeth resemble those of probos- 

 cideans, especially in manner of replacement — i.e., by loss of most 

 anterior tooth and development of a new tooth at hind end of row. The 

 total number produced in one half-jaw may exceed 20, but not more 

 than 6 are in use at one time. 



