692 MAMMALIA. 



MANATEE (Manatus}. DUGONG (Halicore). 



Neck vertebras reduced to s\x. The usual seven neck vertebras. 



Abortive incisors (|) in both sexes. Two tusk-like incisors persist in the 



the male. 



Molars (Li) six or so at a time, Molars (4 or . } 2 or 3 at a time), 

 uniform, with square enamelled primitive, with persistent pulps 



crowns, and tuberculated trans- and no enamel, 



verse grinding ridges. 



Premaxillas almost straight. Premaxillas crooked downwards. 



Tail rounded. Deeply notched tail. 



Rudimentary nails on fingers. Nailless digits. 



Caecum divided. Thick and single caecum. 



M. australis and M. senegalensis H. tabernaculi, E. African coast 

 live in the mouths of great rivers and Red Sea ; H. dugong, Indian 



which flow into the tropical and Pacific Oceans, eastward 



Atlantic. from the home of the last species 



to the Philippines; H. australis, 

 E. and N. Australia. 



The genus Rhytina was toothless, with a slightly crooked snout, small 

 head and arms, and thick naked skin. Steller's Sea Cow (R. stelleri], 

 the only known species, from the North Pacific, seems to have been 

 exterminated in the last century. 



The order was once much larger. Fossil forms occur in Tertiary strata. 

 The most important is Halitherittm, a less specialised Sirenian than 

 those still extant, e.g., with traces of hind limbs. 



Order 3. UNGULATA. 



Hoofed Animals Artiodactyla, Perissodactyla, Hyra- 

 coidea, Proboscidea, and extinct sub-orders. 



This large and somewhat heterogeneous order includes 

 pigs, hippopotamus, camels, cattle, deer, tapirs, rhinoceros, 

 horses, hyrax, elephants, and some other distinct types. 



They are terrestrial, and for the most part herbivorous 

 animals. Their digits generally end in hoofs or at least in 

 broad nails. In the adults of the modern types there are no 

 clavicles. The teeth are diverse, the milk set in part 

 persistent until the animal attains maturity. 



Ungulata Vera : ARTIODACTYLA and PERISSODACTYLA. 



In these typical Ungulates, the feet are never plantigrade. 

 In modern types there are never more than four functional 

 toes. The os magnum of the carpus articulates freely with 

 the scaphoid. The brain is well convoluted. The testes 

 descend into a scrotum. The uterus is bicornuate. The 

 placenta is non-deciduate,and either diffuse or cotyledonary. 



