AVES; MAMMALIA 955 



them. The StrutJiioncs, or ostriches, rheas, cassowaries and emus 

 are all large, flightless birds with small wings, a keelless sternum, 

 and well-developed walking legs. They also include the extinct 

 -(^pyornis and the equally extinct moas (Dinoniithida:), without or 

 with extremely rudimentary wings and pectoral arch and with 

 massive legs. The StrutJiioncs appear first in the Tertiary. The 

 New Zealand Apteryx, a small flightless bird, represents the order 

 Apteryges and the living tinamous the order Cr\pturi. Both have 

 only fragmentary fossil representatives. The super-order Euorni- 

 thes, with 13 orders, includes most of the existing birds. A few 

 representatives (cormorants, etc.) occur in the Cretacic, but the 

 great majority of types are not known before the Eocenic and 

 many not until later. 



Mammalia. 



The mammals are warm-blooded animals with the body typically 

 covered by hair, and in nearly all cases they bring forth their 

 young alive, the monotremes alone laying eggs. All, however, 

 suckle their young. The marsupials (opossum, kangaroo, etc.) 

 bear their young in an immature state, and these are then placed in a 

 pouch or marsupium. The placental mammals bear perfect young. 

 The Insectiz'ora go back to the Eocenic ; they comprise the moles, 

 shrews, hedgehogs, etc. The Chiroptera, or bats, also go back 

 to the Eocenic. The Dermoptera are characterized by a cutaneous 

 expansion, extending from the wrists to the ankles and forming a 

 parachute. They are generally called flying lemurs and are un- 

 known in a fossil form. The Edentata, chiefly restricted to South 

 America, are nearly or quite toothless and include the living ant- 

 eaters and sloths, the armadillos, with jointed armor, and the ex- 

 tinct Glyptodon with solid armor. Here also belong the giant 

 sloths, the Megatherium, the Mylodon, and Grypotherium — all of 

 them but recently extinct. 



The Rodentia comprise the gnawing types with long, sharp 

 curved incisors. They go back to the Eocenic. The Tillodontia 

 are extinct forms from the North American Eocenic. They are 

 related to the rodents. The Carnivora, or flesh-eaters, comprise a 

 large number of living and extinct types, such as the Creodontia, 

 of the Tertiary; the Fissipedia, including Canidcc (dogs), Ursidcc 

 (bears), Viverridcc, Mustclidcc (otters, etc.), Hyccnidcc (Hyaenas) 

 and Felid(V (cats, tigers, lions, panthers, etc.) ; and the Pinnipedia, 

 or marine carnivores, such as seals, sealions, etc. Many of these 

 have representatives in the Tertiary. The Cetacca. o.r whales, dol- 



