438 



THE GENERAL PRINCIPLES OF ZOOLOGY 



elephant. These birds are called the moas and have certainly 

 become extinct since man inhabited the earth. Their skeletons 

 are very numerous in the most recent deposits. Other birds 

 have been found in the Post-tertiary of Madagascar which 

 rivaled the moas in size. With the bones of the genus 

 /Epyornis have been found eggs measuring thirty-five centi- 

 meters in diameter. Some birds have become extinct within 

 very recent times, such as the great auk (Fig. 415) and the 

 dodo (Fig. 416), to which we have already referred. 



FlG. 415. Alca impennis, the gn.it auk, now extinct, and the smaller Alca {Utamania} 

 torda, the razor-billed auk. (From a photograph provided by the American Museum of 

 Natural History.) 



The first remains of the Monotremata are found in the 

 Pleistocene of Australia, and the species living then differ 

 little except in size from the Australian Echidna of to-day. 

 Of the Marsupialia the opossums have been found in the Ter- 

 tiary of both Europe and America, and in the Pleistocene of 

 America only. In the Tertiary of South America are remains 

 of a genus of large marsupials, Diprotodon. All fossil mar- 

 supials except the Tertiarv belong to the Pleistocene and 

 appear to be confined to Australia ; the genus Diprotodon is 

 represented here also, and attained the size of a rhinoceros. 



