146 Transactions. — Zoology. 



due to their being unable to fly ; and the only alternative is 

 that they crossed by swimming. But, although the emu and 

 the rhea are both said to take readily to water many 

 placental mammals do the same, and it is very unlikely that 

 the struthious birds should twice have swum across straits— 

 once from the Oriental to the Australian region, and again 

 from the Australian region to New Zealand— which were im- 

 passable to mammals. There are also other^ reasons tor 

 doubting the northern origin of the Australasian Eatitae. ine 

 struthious birds of New Zealand, notwithstandmg the almost 

 complete absence of wings, make a nearer approach to the 

 ori<^inal stock— that is, are less modified— than any ot the 

 other families. This is shown by the long lateral processes 

 of the sternum, by the smaller coraco-scapular angle m tlie 

 smaller species, by the broad sacrum and free ischia and 

 pubes, as well as by the hind-toe. Again, the_ only small 

 Eatitai are from New Zealand ; and, if the group is descended 

 from flying birds, the smaller forms must have preceded the 

 larger ones. We should expect to find the least altered forms 

 near the place of origin; and, if the New Zealand Eatitae 

 have migrated from Europe or Asia, how comes it that the 

 least-modified forms have been gathered together m these 

 Islands '> Flightless birds are generally developed on islands 

 where there are no mammals, and not on large continents 



The common ancestors of the Australian and New Zea and 

 Eatitai must have had both wings and hind-toes hke the kiwi 

 and Palaptenjx. Probably they also had, like the moas, 

 feathers sometimes with one, sometimes witn two, shafts to a 

 quill Palavteryx makes the nearest approach to the common 

 ancestor of the Australasian Eatit® of any bird we know , _but 

 no doubt these common ancestors had much larger wuigsthan 

 Palavteryx, and they must have possessed clavic es. i he late 

 Professor W. K.Parker long ago pointed out the struthious 

 affinities of the tinamous,=:= and lately he has proposed to 

 place the Eatitse, and perhaps Opisthocoinus y^ith the lina- 

 fuida^ in the group Droma^omorphae of Huxley.i The tinamous 

 are birds about the size of kiwis, living m Centra and South 

 America, and they show in the free ischia and pubes, as we 1 

 as in having a free post-axial tarsal bone, a decided approach 

 to the Dinornithida^. Probably, therefore, the Australasian 

 Eatit£e are descended from birds allied to the tinamous, winch, 

 beino- carinate and with large wings, found their way to New 

 Zealand by flight, like all the other birds. 



There are no great difficulties in accounting for a migration 

 by land of these birds from New Zealand into Austraha, while 



* Trans. Zool. Soc, vol. v., p. 149 (1866). 

 t Trans. Zool. Soc, vol. xiii., p. 80 (1891). 



