MIOCENE PERIOD 165 



variety, consisting chiefly of small opossums (Microbiotherium), 

 and somewhat phalanger-toothed opossum-rats (Palaothentes, 



Marsupials seem also to have been but scantily represented 

 on the northern continent. In Europe they had long been 

 on the decline ; and the opossums of the Oligocene Period 

 were, so far as is known, the last of pouched life on that 

 continent. 



In Australia this ancient Order was probably full of vigour 

 and abounding in a variety of forms, as its development 

 had not been complicated by mammals of higher type. 

 Evidence, however, is wanting as to the condition of Miocene 

 marsupials in that part of the world. 



If, as there is every reason to believe, no mammals of WHALES 

 higher rank than marsupials were living in Australia, such, 

 in the form of whales, were flourishing off her coasts. These 

 were creatures of the newer fashion, such as had come into 

 view in the last Period (Prosqualodon, Squalodori). The 

 Zeuglodonts the earliest known whales apparently had 

 now quite died out. During the last Period they had been 

 dwindling in numbers, and the new divergent forms, more 

 nearly resembling the toothed whales of to-day, had become 

 well established. In South American waters some forms of 

 a still more advanced type were in existence. These may be 

 described as sperm whales, although they differed from 

 their present-day descendants in having their teeth ena- 

 melled, and, moreover, in possessing teeth in the upper as 

 well as the lower jaw (Physodon). Other forms apparently 

 were in a condition between toothed whales and whalebone 

 whales (Argyrocetus} ; and a few seem to have reached a 

 stage constituting them whales of the latter category (Ceto- 

 therium). In European waters some members of the " white 

 whale " genus of the Dolphin family were in evidence (Del- 

 phinapterus). Here also were whales, some qualifying for 

 " Bottle-nose," some for " Hump-back " distinction ; but 

 the special features, it would seem, were not fully developed 

 until the next Period (Hyperoodon, Megaptera). 



The success of the seaward move of some ancient land- 

 mammals was, it will be admitted, beyond question. Con- 



