MAMMALIA. 561 



thus there are no teeth, the mandible is much reduced, the jaws are 

 long and tapering, the mouth small and the tongue long and mobile. 

 The limbs are short and the claws long and powerful. The Pangolins 

 are found in East Africa and in the Oriental region (India), and comprise 

 one genus. 



Like the Xenarthra, the JVomarthra are very low types 



of Eutheria, which affect an arboreal or fossorial habit. 



They are confined to Arctogoea, just as the Xenarthra are 

 confined to Neogcea. 



Order VI. — Sirenia. 



The Sirenia are aquatic herbivorous animals known as 

 the Manatees and Dugongs, or sometimes collectively as 

 the Sea-cows. They live either in rivers or at the river- 

 mouth, and, although well adapted for aquatic habit, they 

 do not quite reach the same stage in this direction as the 

 Cetacea. As in the latter, the body is more or less fish- 

 like with tapering tail ending in a horizontal "fluke," there 

 is little or no hair and no pinna to the ear, the fore-limbs are 

 in the form of flippers and the hind-limbs are absent. The 

 valvular external nares open far back towards the top of the 

 head, resulting in the formation of a rostrum, and there are 

 retia mirabilia in parts of the body. In all these anatomical 

 features the Sirenia are like the Cetacea^ but here the resem- 

 blance ends. The cervical vertebrae are never fused to- 

 gether, the teeth are neither absent nor homodont and the 

 food consists of aquatic weeds. The flippers usually have no 

 more than the normal number of phalanges''' (2.3.3.3.3.) and 

 the joints of the fore- limb are largely functional, as the flipper 

 is used not only for swimming but for assisting food to the 

 mouth, and in some cases possibly in holding the young. 

 In copnparing these characters with the porpoise, it will 

 clearly be seen that the Sirenia have not progressed quite 

 so far in adaptation as the Cetacea. Other special points in 

 the anatomy show that there is no true genetic connection 

 between the two orders. 



In Sireriia there is the same tendency to disappearance 

 of the front teeth as we have noticed in the Edentata, 

 The manatees have no functional incisors nor canines 



* Rarely four. 



M. 37 



