EASTMAN: REMAINS OF STRUTHIOLITHUS CHERSONENSIS. 141 
Turning now to the advent of the moa into New Zealand, and of 
Apyornis upon the island of Madagascar, we note that previous writers 
have essayed in various ways to meet the following dilemma. If these 
birds migrated from what is now the mainland prior to the Tertiary, why 
have not their remains been found in strata older than the Pliocene ? 
Or, if the islands remained inaccessible to them until the late Tertiary, 
how was the passage finally accomplished by wingless birds? And what 
is still more to the point, why were they in the latter event unaccompa- 
nied by placental mammals? Of the two principal theories put forward 
to explain the facts, neither, in the opinion of the present writer, suffi- 
ciently accounts for all the difficulties. In the case of the moas, Mr. 
Wallace * supposes that their ancestors either flew or swam across straits 
impassable to contemporaneous mammals. But Captain Hutton prop- 
erly takes exception to this view, on the ground that their Ratite 
characters are due to their being unable to fly ; moreover, the oldest 
known moas were entirely without wing bones, and possessed a very 
rudimentary shoulder girdle. As to the alternative explanation that 
they crossed by swimming, Captain Hutton? remarks as follows: “ But, 
although the emeu 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 the same straits — once 
from the Oriental to the Australian region, and again from the Austra- 
lian to New Zealand — which were impassable to mammals. There are 
also other reasons for doubting the northern origin of the Australasian 
Ratite.” 
Now, as most persons are aware, both biological and geological evi- 
dence go to show that New Zealand has been separated from Australia, 
and Madagascar from Africa, at all events ever since the dawn of the 
Tertiary, and probably since the latter part of the Cretaceous. Accord- 
ingly, Captain Hutton supposes, after having shown the improbability 
of wingless birds either flying or swimming across straits, that the moas 
have had a different origin from the rest of the Ratite,—an opinion 
from which we find no reason to dissent, although rejecting his hypothe- 
sis of a tinamou-like ancestor in the Eocene, and a submerged Antarctic 
continent. Although the oldest known remains of the Dinornithide are 
of Miocene age, and no one has attributed to the family an earlier origin 
than the Eocene, yet the occurrence of moa remains on the continent of 
1 Wallace, A. R., Island Life, 2d edition, p. 481, 1892. 
2 Hutton, F. W., The Moas of New Zealand (Trans. New Zealand Inst., Vol. 
XXIV. p. 147), 1891. 
VOL. XXXII. — NO. 7. 2 
