56 THE LESSON OF EVOLUTION 



Greenland. The specimens are very fragmentary ; 

 but all appear to have been arborescent, like the 

 bamboos of the present day. None are known with 

 certainty from the lower Eocene, a few appear in 

 the upper Eocene ; but in the Oligocene and Miocene 

 herbaceous grasses are abundant. It also appears 

 that none of the Eocene mammals have their teeth 

 specially adapted for eating grasses ; but that they 

 gradually became modified in this direction during 

 the Miocene. 



The first known butterflies and bees are from the 

 Eocene, but insects were not abundant before the 

 Oligocene. Sea-snakes occur in the Eocene, and 

 land tortoises in the Miocene. The great develop- 

 ment of birds was very remarkable ; for the remains 

 of all the existing orders of Carinata3 have been 

 found in the Oligocene, except divers, gulls, pigeons, 

 and parrots ; and these are recorded from the 

 Miocene. All the Miocene and many of the Oligo- 

 cene birds appear to belong to genera still existing. 



Of the mammalia the multituberculata died out 

 in the Cainozoic (Miocene?) of Patagonia. The 

 metatheria are represented in the Eocene of the 

 northern hemisphere by several forms of polyproto- 

 dont marsupials ; but they w y ere quite overshadowed 

 by the eutheria. It was in the southern hemisphere 

 that the marsupials flourished, and gave rise to the 

 diprotodont section, which is known only from Aus- 

 tralia and South America. The eutheria, or 

 placental mammals, suddenly appear in abundance 

 in the lower Eocene; and, before the close of that 

 period, most of the existing orders were represented, 



