644 CHORD ATA. 



long proboscis with a finger-like process at the tip, lastly by 

 the dentition. Canines are entirely lacking, but the incisors of 

 the upper jaw have pulps and therefore continue to grow 

 throughout life, forming the well-known tusks. In the living 

 elephants there are but a single pair of tusks, but in some extinct 

 Mastodons there were a second smaller pair in the lower jaw, while 



in Dinotherium only the lower in- 

 cisors were developed, these pro- 

 jecting downwards. The molars 

 (in Mastodon and Dinotherium 

 with normal replacement and 

 cusps) consist of numerous plates 

 of enamel and dentine united 

 FiG.667.-inside~71e7t lower jaw of b J cement, and undergo a lateral 

 Sff owenri, fuLtfon^mXr; 6 !; displacement. Of the three large 

 its successor. molars and premolars only one 



at a time is functional (fig. 667, ./); when worn out the next one 

 behind (2) takes its place. Further features are a uterus bicornis, 

 a zonary placenta, and two pectoral mammas. 



ELEPHANTINE : Elephas indicus, small ears ; E. africanus, large 

 ears. E. primigenius, mammoth, in the pleistocene ; specimens found 

 frozen in ice in Siberia have close woolly hair, in some places three feet 

 long. Mastodon, with tuberculate teeth, range from miocene through the 

 pliocene. DINOTHERIDJE, only lower incisors ; Dinotherium, Old World 

 miocene. 



Order VII. Hyracoidea. 



The single genus Hyrax, including species from western Asia 

 and Africa, with four-toed front feet, hind feet with three toes, 

 the digits with nails, the placenta zonary, and the dentition |~f , 

 forms this group, no fossils being known. Hyrax syriacus is sup- 

 posed to be the ' coney ' of the Bible. 



Order VIII. Sirenia. 



This order consists of a few aquatic mammals which are whale- 

 like in form, with the fore limbs fin-like, the hind legs lacking, and 

 a horizontal caudal fin. They live in shallow seas or in the 

 mouths of rivers, where they feed on the tang, which they chew 

 with jaws covered with horny plates. The teeth (in the fossil 

 Prorostomus f yf-f ) are reduced or entirely lacking. The fore legs 

 are pentadactyle and often have rudimentary nails and always a 

 flexible elbow. The two pectoral mammae have possibly caused 

 these animals to furnish the germ of truth in the mermaid myth. 

 Manatus americanus,* the manatee, six cervical vertebrae, eight to 



