MAMMALIA 305 



667. The Sirenia are herbivorous marine mammals. The anterior 

 appendages are paddle like, the posterior rudimentary. Manatee, dugong, 

 sea cow. 



668. The Primates have a heterodont dentition, all appendages have 

 five digits. The nails are flat. The eyes are directed forward. Sub- 

 order Prosimiae; the teeth similar to those of Insectivores, the wall of the 

 orbit incomplete laterally. Lemurs. Sub-order Simiae; the incisors are 

 chisel shaped, the orbit wall complete. Monkeys and apes. 



Section i. Platyrhina; the flat nose monkeys of South America. 

 Section 2. Catarrhina; the monkeys, mandrels, gibbons, orang- 

 utan, chimpanzie and gorilla. 



669. Finally the genus Homo is placed by some authors in an order by 

 itself, the order Bimana. Others place this genus in a family, Hominidae, 

 under the order Primates. The genus is regarded as containing only one 

 living species, Homo sapiens, which is sub-divided into races. 



