includes, broadly, tropical America. The forms found here bear certain
resemblances to those found in the two regions already discussed; but
this resemblance is probably rather because they are low in the scale of
development than that there has ever been any direct land connection
between them. Much the same conditions of life must have prevailed for
all, thus making the rate of development nearly equal. Here we find the
rhea, tinamou and hoactzin, which show low grade; but mingling freely
with them the higher forms which seem to have come down from the north
later and all but crowded out these lower ones. There is abundant
evidence that the struggle for existence in South America has been far
less severe than in North America.