Button.— 07i the Moas of New Zealand. 149 



which were united in the older PHocene, and ultimately it 

 divided into the two islands which we have now. If the 

 ancestors of the moas inhabited New Zealand during the 

 Eocene period -as we have seen was most probably the case 

 —each island m the Miocene may have contained a different 

 kind of moa, all of which would mingle together when the 

 land rose m early Pliocene times. In the newer Pliocene the 

 birds must have been again separated by the formation of 

 Cook htrait, and the species in each island would again be 

 isolated from each other. 



^ I still think that isolation during Miocene times gave 

 origin to the genera; but variations of specific importance 

 have m several cases taken place since the formation of 

 Cook Strait, and most of the species must be due solely to 

 variation without isolation. As is the case with most com- 

 mon_ species, the moas varied greatly, and, there being no 

 carnivorous mammals or other powerful enemy to hold them 

 m check, while vegetable food abounded in all directions 

 natural selection did not come into play, the intermediate 

 forms were not strictly eliminated, and, consequently, the 

 different species were not distinctly marked off, but one 

 merged into the other. Under such favourable circumstances 

 the conditions of life were very easy, and the birds got larger 

 and tatter, more sluggish and more stupid. 



If the moas are descended from flying birds, which we 

 cannot doubt, it is evident that the smaller species must have 

 preceded the large ones; and this is borne out by the facts of 

 geographical distribution. For it is only the smaller species 

 of Anomaloptenjx, Mesopteryx, Syornis, and Dmornis which 

 are found m both Islands, the larger forms in Syornis and in 

 Vmomis h^vmg been developed since the Islands were sepa- 

 rated. Whether the apparently allied species of Dinornis are 

 really geographical representatives of each other, due to isola- 

 tion, or whether they form two separate lines, one in each 

 island, diverging from D. struthioides, we cannot say until the 

 skulls and sterna of the North Island species are known • but 

 the latter hypothesis seems to me to be the more probable, as 

 It accounts for all the species of the South Island being more 

 robust than those from the North Island. When we try by 

 morphological evidence to reconstruct the genealogy of the 

 moas we see that Ilesoptenjx connects Gela with Syor7us, 

 tliat It IS Itself connected with Euryapteryx by Auomalopterzjx, 

 and tfiat this last genus is connected with Dmornis by Pala- 

 ptejl'x Evidently Anovialopteryx and Palapteryx are the 

 oldest forms : but, if Palapteryx had wings, it could not have 

 been derived from the wingless Anomaloptcryx ; and, if the 

 birds were increasing m size, Anomaloptcryx could not have 

 been derived from Palapteryx. Both must have had a com- 



