366 PROCEEDINGS OF SECTION D. 



somewhat on the present Ratite pattern, but that pattern 

 appears to have been at the time common to all birds, and 

 the typical skull of the true CarinateB was not developed 

 until later, probably not until the Middle Eocene. Pre- 

 viously, in the Upper Cretaceous and Lower Eocene, there 

 were no true Carinato!. Although many of the birds had 

 keeled sterna, they all belonged to the Proto-Carinatce of 

 Professor T. J. Parker, of which the Tinamous and Opis- 

 thocomus of Central America are still living representatives. 

 That the Ratita are descended from flying birds is now 

 generally allowed, but the characters which are used to unite 

 them all into one group are either early Proto-carinatce 

 characters or else are merely adaptations to terrestrial habits, 

 and consequently of little value as evidence of affinity. It 

 is therefore possible that the Raiitce may have had more 

 than one origin, although all have sprung from the Proto- 

 carinatce, as indeed have all living birds. 



If the Patitce have a. single origin, and if the Gastor- 

 nithidcB belong to the RatitcB, then no doubt the Ratitce 

 originated in the north and spread to the south, but if either 

 of these statements is wrong the conclusion does not follow. 



Now, by Mr. Wallace's hypothesis there are great diffi- 

 culties in explaining how the Struthious birds reached 

 Australia and New Zealand unaccompanied by placental 

 mammals. We cannot suppose that they preceded the 

 mammals, because so far as we know the placental mam- 

 malia are older than the Ratitce. Neither can we suppose 

 that they flew over a strait which was impassable to the 

 mammals, because no bird that could fly could be admitted 

 into the Ratitce, the special characters of the group being* 

 due to their being unable to fly. The only alternative is that 

 they swam across such a strait. But, although the emu is 

 said to take readily to water, so also do many of the 

 mammalia, and it is very unlikely that the Struthious birds 

 should have twice swam across straits — once from the 

 Oriental to the Australian region, and again from the Aus- 

 tralian region to New Zealand — which were impassable to all 

 the mammalia. 



There are also other reasons for doubting the northern 

 origin of the Australasian Ratit(E. The Struthious birds of 

 New Zealand, including the lately extinct moas, make a 

 nearer approach than do any of the other families to the 

 original stock. This is shown by the lateral processes of the 

 sternum, the free ischia and pulies, and the hind toe ; and 



