EASTMAN: REMAINS OF STRUTHIOLITHUS CHERSONENSIS. 139 
Strong enough arguments, we think, have been put forward to show 
that the theory of a common origin of the Ratite is untenable, and 
hence no single hypothesis of distribution is able to account for the facts 
of their distribution. We cannot imagine a race of ostriches sprung 
from Hesperornis or anything of like nature in the Cretaceous, spreading 
over the whole earth in the Tertiary, and then, as decay set in, leaving 
its fragments scattered in remote corners of the globe. But the prob- 
lems presented by the alternative theory, that of multiple origin, are 
none the less interesting or important, althongh decidedly more compli- 
cated. To seek the nearest Carinate affinities for the different sections 
of Ratite separately ; to develop the palzeontological history of each 
more fully; and to inquire into the physical and biological conditions 
which led to their insulation, perpetuation, and differentiation in various 
provinces, — these are only a few of the points that invite an extended 
investigation. Some of the problems have already been touched upon, 
notably as regards the origin of the moas, the South American ostrich, 
and Apyornis ; and we may profitably turn our attention for a moment 
in this direction, beginning with Rhea. 
No one can deny that the physical resemblances between Ahea and 
Struthio are very great; in fact, the popular term “South American os- 
trich ” is an obvious commentary on their similarity. Although both 
genera are regarded as typical of distinct families, and are even com- 
monly placed in separate suborders, yet, if one were asked to specify the 
nearest living ally of the African ostrich, he would unhesitatingly point 
to Rhea. Only two interpretations of structural resemblances are pos- 
sible: either they indicate direct genetic relationships, or we have here 
a most remarkable case of convergence. Now in this instance we confess 
to sharing Dr. Lyddeker’s prejudice against the theory of parallel devel- 
opment, already quoted, as there is too striking a coincidence in the 
forms produced to be explained as the result of adaptation during recent 
times in two widely distant regions of the globe. The natural and only 
logical plan would be to assume blood relationship between J?he and 
Struthio as a matter of course, until it is proved that by no possibility 
could they have been derived from the same ancestral stock. Now if 
Rhea had different progenitors from the ostrich, we are in utter ignorance 
as to what they were like, as no other descendants remain. That there is 
anything in common between hea and the tinamous we cannot believe 
for a moment, in view of the different organization of the latter. Hence, 
Captain Hutton’s theory, which derives both Rhea and the moas from 
a tinamou-like ancestor which crossed into Australia and New Zealand 
