110 



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in the south of Europe. At present, species exist on the 

 shores of the continents in the warmer latitudes. (Fig. 46.) 

 The succession of types in this order is measured by 

 the modifications in the dentition. In the Eocene Pro- 

 rastomidse we have a nearly normal dentition with dis- 

 tinct canines. In the succeeding forms canines are want- 

 ing and the incisors are either enlarged or disappear. 

 Thus, in the Neocene Halitheriidse we have nearly nor- 

 mal molar dentition, with incisors reduced in number and 

 functioning as- digging tusks. The existing dugongs con- 

 tinue the enlarged incisors, but the molars are reduced in 

 number, and have become simple prisms. The also 

 existing Manatees have lost the incisors, retaining nor- 

 mal molars which have abnormally increased in number. 

 In the lately extinct Rhytinidse all dentition has disap- 

 peared. 



The Edentata have been generally restricted to the 

 Southern Hemisphere, although during the Neocene they 

 ranged as far north as the .^gean Sea in Europe, and to 

 latitude 46° in North America during the Plistocene. They 

 first appear, in the Eocene of Patagonia, and were ex- 

 tremely common in the Neocene throughout tropical 

 America, where they are still abundantly represented. 

 A few species still remain in the Ethiopean and Paleo- 

 tropical geographical realms. The Megatheriidse of the 

 South American Neocene were of large and gigantic size, 

 the largest species pertaining to the genus Megatherium, 

 which ranged in North America to South Carolina. The 

 Glyptodontidse were covered with an. immovable carapace 

 consisting of bony tesserse, somewhat like that of arma- 

 dillos. They varied in size from that of a sheep to that 

 of a rhinoceros. Species were abundant in the Neocene of 

 South America, when they also ranged north to Texas, 

 Florida, and Kansas. The most ancient (Eocene) Edentata 

 display traces of enamel on the teeth. 



