INTRODUCTION 7 



(A) Prototheria.— Very primitive, egg-laying (oviparous) 

 mammals. Represented in modern times by the duck- 

 bill (Ornithorhynchus) and spiny ant-eater (Echidna) 

 of Australia. Upper Triassic to modern times. 



(B) Eutheria.— Viviparous mammals with anus and uro- 

 genital openings distinct. 



a Didelphia (JMarsupialia) : Pouched mammals. Typically carry- 

 mg the young in a pouch; placenta rudimentary or primitive. 

 Jurassic to modern. The modern r'epresentatives are the opos- 

 sums and kangaroos. 



^ Monodelphia (Placentalia) : Young nourished before birth by a 

 placenta; never carried in pouch. 



(A) Unguiculata.— Clawed placental mammals. 

 Mesozoic to modern. Adapted to terrestrial, fos- 

 sorial, arboreal, aquatic, cursorial, and volant life. 



1. Insectivora.— (Moles, shrews, and hedgehogs.) 

 Eocene to modern. 



2. Chiropkra.—{Bsits). Miocene to modern. 



3. Carnivora. — Eocene to modern. Modern forms 

 under two suborders: 



{a) Fissipedia. — Dogs, raccoons, bears, wea- 

 sels and the cats, hyenas, etc. 

 {b) Pinnipedia. — Seals, walruses, etc. 

 4- Rodentia. — Rabbits, squirrels, beavers, rats, 

 mice, and porcupines. Oligocene to modern. 

 5. Edentata.— 'Cloths, ant-eaters, and armadillos. 

 Miocene to modern. 

 (5) Primates.— Fingers terminating in ''nails" as 

 distinguished from mammals with claws (un- 

 guiculates) or hoofs (ungulates). Eocene to 

 modern. Adapted to arboreal and ambulatory 

 life. Lemuroids, lemurs, monkeys, apes and man. 

 Probably arose from shrew-like insectivores. 

 (C) Ungulata.— Hoofed mammals. Eocene to mod- 

 ern. The Condylarthra and other primitive and 



