( 84) 



Upper Eocene to the Ipi.t-i Miocene; bul, on the other hand, there is nothing in 

 their present fauna to show that since their hist emergence they have been connected 

 with any land area whatever. On the contrary, it seems clear that since that period 

 they have never been united even with New Zealand, for not a trace of any of the 

 Dinornilhidae, Aptery.c, Cnemiornis, Aptoniis, or any of tlie flightless birds charac- 

 teristic of those islands have been foimd in them. Jloreover, as Mr. Forbes himself 

 has pointed out, no fragment of the skeleton of D'wphoraptei-yx is recorded from 

 New Zealand. This complete difiference in the flightless birds of the two areas 

 does not seem to be outweighed by the oecmTence of Hatteii-ia, remains of which 

 Mr. Forbes states he has found on Wharekauri, the main island ; indeed, since in the 

 whole of the immense collection of bones at the Tring JMuseum no reptilian remains 

 occur, it seems possible that this determination may be due to a mistake. Dr. Gadow* 

 has, I think, given the true exijlanation of the hkeness of Diaphorapteryx and 

 Aphanapteryx to one another, namely, tliat it is the result of parallelism of evolution, 

 or, in other words, similar conditions acting on similar organisms have produced like 

 results. The ancestors in the two cases, generalised rails capable of flight, were 

 probably of different genera, or, at least, species. In the case of Bmphorapteryx this 

 ancestor was most likely some widely spread form, such as Hypotaenidia phili2ypinensi8 

 is at the present day, individuals of which from time to time reached New Zealand, 

 Lord Howe Island, and the Chatham Islands, the channels between which may 

 formerly have been narrower than at present. The modified descendants of these 

 birds are now refen-ed to the genera Diaphorapteryx, Cahcdus, and Ocydrmiius, the 

 most highly modified forms being the outcome of earlier, the less altered of later 

 colonisations. In any ca-<e there can be little doubt that these rails became flightless 

 in the islands they now inhabit, and cannot therefore be regarded as evidence of the 

 former extension of laud ; in other words, they are of no value in determining former 

 geographical conditions, since they are themselves the oiatcome of the present one. 



* Bronii's Thierriifli, Arcs, Vol. 1 1. (Systcniatischer Thcil.). ]■. UH. 



le MAR ;396 



