26 THE AGE OF MAMMALS 



A. EGG-LAYING :\IAMMALS. Very Primitive, Reptile-like, or 



Transitional, Reproducing their Young from Deposited Eggs. 



I. PROTOTHERIA. 



1. Protodonta. Very small and primitive, North American niain- 



niiUs ('.■') of the early Age of Reptiles. 



2. MONOTREMATA. Of Australia, New Guinea, and Tasmania, highly 



specialized Prototheria. No Pre-Pleistocene forms certainly known. 

 Duckbill Platypus (^Omilhor/iipichus) and Spiny Anteater (Echidna). 



B. VIVIPAROUS MAMMALS. Of Higher Grade, Bringing Forth 



their Young Alive. 



II. MARSUPIALIA, DIDELPHIA, or METATHERIA. Pouched Mammals, 



or ^larsupials, typically carrying tlie young in a pouch. Placental 

 structure rudimentary or primitive. Extinct and living families of 

 Australia, South America, and (opossums, etc.) Holarctica. 



1. Triconodonta. Polyprotodont carnivorous marsupials (?) of the 



Age of Reptiles. 



2. MARSUPIALIA PROPER. 



a. Multituberculnta. Diprotodont, herbivorous marsupials of the Age of 



Reptiles and early Age of Mammals. 



b. Poli/protodontia. Polyprotodont, carnivorous, and omnivorous Mar- 



supials of the Age of Mammals. Opossums, dasyures, etc. 



c. Diprotodontia, Diprotodont, herbivorous marsupials of the Age of 



Mammals. Phalangers, kangaroos, etc. 



ni. PLACENTALIA, MONODELPHIA, or EUTHERIA. Mammals nour- 

 ished before birth by a typical placenta. Young never carried in a 

 pouch. 



A. UNGUICULATA. Clawed Mammals, adapted to terrestrial, fossorial, 

 arboreal, aquatic, cursorial, and volant life. Including all the actual 

 and theoretical primitive forms of mammals, as well as many modern- 

 ized or highly specialized forms. 



1. Pantotheria (TRITUBERCULATA). Small primitive insectivores of 



the Age of Reptiles (Jurassic), generally with numerous cheek teeth. 



2. Insectivora. Modern insectivores, such as moles, shrews, hedge- 



hogs, and teiirecs. 



3. Tillodontia. Lower to Middle Eocene, tillotheres or tillodonts, 



herbivorous or phytophagous mammals, in some respects similar to 

 rodents. 



4. Dermoptera. Represented only by the "flying lemur," Galeo- 



pithecus, of the Oriental region. 



5. Chiroptera. The bats, including the fruit bats, vampires, insect- 



eating bats, etc. 



