SURVEY OF THE ORDERS OF RIAMMALIA. 679 



The development of the fertihsed ovum is in most respects 

 like that of the hedgehog (pp. 648-56). In the guinea-pig 

 and some other Rodents, but not in the rabbit, there is a 

 remarkable inversion of the germinal layers. 



There is in the rabbit, as in all Rodents, a provisional 

 yolk sac placenta. The allantoic placenta is discoidal and 

 deciduate. 



Systematic Survey of the Orders of Mammalia. 



I. Sub-Class — Prototheria or Ornithodelphia — Order 



Monotremata. 

 II. „ — Metatheria or Didelphia — Order Mar- 



supialia. 

 III. „ — Eutheria or Monodelphia or Placen- 



TALIA. 



Orders of Eutheria. 



1. Edentata. 



2. Sirenia. 



3. Ungulata. 



Artiodactyla jungulata Vera. 



Perissoclactyla J '^ 



Hyracoidea. 



Proboscidea. 



Extinct sub-orders. 



4. Cetacea. 



Mystacoceti — baleen cetaceans. 

 ArchEeoceti — (extinct types). 

 Odontoceti — toothed cetaceans. 



5. Rodentia. 



Slmplicidentata. 

 Duplicidentata. 



6. Carnivora. 



Carnivora Vera. 

 Pinnipedia. 

 Creodonta (extinct). 



7. Insectivora. 



Insectivora Vera. 

 Dermoptera. 



8. Chiroptera. 



Megacliiroptera. 

 Microchiroptera. 



9. Lemuroidea. | ^ pHmates 

 10. Anthropoidea 



