644 



CHORD AT A. 



Fig. 667.— Inside of left lower jaw of 

 Klephai^ indicium, the alveoli opened. 

 (After Owen.) i, functional molar; 2. 

 its successor. 



at a time is functional (fig. 607, 



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

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

 the ujiper jaw have pnlps 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 

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



in Dinotlieriiuii 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 

 by cement, and undergo a lateral 

 displacement. Of the three large 

 molars and premolars only one 

 1); when worn out the next one 

 behind (5) takes its place. Further features are a uterus bicornis, 

 a zonary placenta, and two j^ectoral mamma3. 



Elephantid.s : Eleplias indicus, small ears ; i?. afrieanus, large 

 ears. ^. primegenius, 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. DiNOTHEElDiE, only lower incisors ; DiiiotJierium, Old "iTorld 

 miocene. 



Order VII. Hyracoidea. 

 The single genus H>/ra:r, including species from western Asia 

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

 tlie digits with nails, the placenta zonary, and the dentition i-jjf, 

 forms this group, no fossils being known. Hi/rax 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 l\^{) are reduced or entirely lacking. The fore legs 

 are pentadactyle and often have rudimentary nails and always a 

 flexible elbow. The two pectoral mammre have piossibly caused 

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

 Maiiatns umericanus,'* the manatee, six cervical vertebra?, eight to 



