340 
ORIGIN OF LIFE IN AMERICA 
the south it was still joined to the Antarctic Continent, which 
had then become separated from Australia. In the north it 
had lost its land connection with North America, which it did 
not regain until later Tertiary times. 
To a certain extent the views of the two authors agree, at 
any rate, in the assumption that the continent of South 
America is composed of several originally independent land- 
masses, one of which was joined to Africa. The most striking 
difference in their opinions, apart from the geological period 
during which the various elements are supposed to have be¬ 
come fused together, lies in Dr. Ortmann’s conception of 
three totally distinct land-masses, while Dr. von Ihering only 
recognises two. Nevertheless, even the latter acknowledges 
the faunistic division of his “ Archiplata ” into a northern 
and southern portion, although his nomenclature is apt to be 
somewhat confusing. Dr. von Ihering informs us (p. 177) 
that the old Archiplata fauna has no close relationship to 
that of the rest of South America. 
A third contribution to the geological history of South 
America is furnished by another group of fresh-water animals, 
namely, the fishes. The tropical American fresh-water fauna, 
having its centre of greatest diversity in the middle Amazon 
basin, says Professor Eigenmann,* is attenuated northward 
till it reaches the vanishing point just on the borders of 
the United States. Southward it extends to somewhere south 
of Buenos Aires. The Patagonian and North American 
faunas are entirely different from the tropical American fauna 
and from each other. The results of his studies are that the 
existing distribution of the fresh-water fishes can only have 
been brought about by the supposition that tropical America 
in early Tertiary times consisted of two land areas (“ Archi- 
guiana ” and “ Archamazona ”), separated by the lower valley 
of the Amazon, which was submerged by the sea. There was 
a land-mass between Africa and South America, possibly 
joining Guiana and tropical Africa. But this connection, he 
urges, must have ceased to exist before the origin of the 
present genera, and even before that of some of the families. 
* Eigenmann, C. H., “ Freshwater Fishes of South America,” pp.;517 
—52S. 
