374 
ORIGIN OF LIFE IN AMERICA 
explain their present range by a direct land bridge between 
the two continents. The American ostrich (Rhea) is only 
known fossil from superficial deposits, but the ostrich (Stru- 
thio) occurs in the Miocene or Lower Pliocene of the Siwaliks 
of India and of the island of Samos. Since the ostrich once 
lived in the Mediterranean region, it is possible that the 
common ancestor of the two families may have utilised the 
mid-Atlantic land bridge to travel from the Old World to 
the New or vice versa. 
The reptiles and amphibians, as Dr. Blanford * has pointed 
out, indicate a much more pronounced faunal relationship 
between South America and Africa than the birds or mammals 
do. Professor Pfeffer f endeavoured to explain this very inge¬ 
niously by the assumption of a former sub-universal, or 
almost universal, distribution and. a subsequent extinction on 
the northern continents. He admits that some form of 
land bridge was necessary, of course, yet almost all inter¬ 
continental communication must have passed, according 
to his views, across a Bering Strait land bridge. He 
quotes a number of instances of groups which are now 
confined to the southern hemisphere, but have once also 
extended to the northern continents, and because they 
have done so he contends that they must have had a 
suh-universal distribution. All those examples which are 
not found fossil in the northern hemisphere are nevertheless 
supposed to have had a similar range and to have gained their 
present southern distribution in different countries by wander¬ 
ing from one to the other almost by way of the North Pole and 
then south again. Nothing but a careful general study of 
existing distribution can convince us of the fallacy of such 
an assumption. 
Let us take, for instance, the family of fresh-water tortoises, 
the Pelomedusidae. It is confined to Africa, including Mada¬ 
gascar, and South America. Curiously enough, one of the 
genera of this family, viz., Podocnemis at present inhabits 
only northern South America and Madagascar. But, as Pro¬ 
fessor Pfeffer tells us, the genus is known as far back as 
* Blanford, W. T., “ Anniversary Address,” pp. 70 — 71. 
f Pfeffer, G., “ Zoogeographische Beziehungen,” pp. 417—418, 
