34 FOSSIL TURTLES OF NORTH AMERICA. 
inhabited by these land tortoises, presents only two very restricted areas. ho at 
that time it abounded in representatives of the family, some of them of gigantic size, 
it is now poor in species, there being only 3. Almost the whole of South America 
is occupied by the family, but there are only 3 known species. Europe claims 
2 species; while Asia possesses 7. Africa is the headquarters of the family, at 
least 20 species occurring on that continent. These belong to 3 recognized genera. 
‘The most remarkable f(ocue of the distribution of the Vestudinid is the occurrence 
of species, some of great size, on islands far away from any large body of land, as the 
Galapagos Islands Bind islands in the Indian Ocean. For purer discussion of this 
subject the reader is referred to the treatment of the family on a succeeding page. 
The geographical distribution of the Pleurodira is represented by fig. 15. It 
will be seen that the species are almost wholly residents of the torrid and dhe south 
temperate zones. A single species has an outlying colony on the ‘Tropic of Cancer, 
at the head of the Red Sea. The wide distribution of these turtles is not surprising, 
seeing that they are a very ancient group. The earliest species that are known to 
S 
belong to the superfamily are described in the present work and come from the 
Upper Cretaceous of New Jersey and New Mexico. 
Doubtless the group existed 
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Fic. 15.—Map showing the distribution of the Pleurodira. 
during the Lower Cretaceous and probably during the Jurassic. In those early 
days the land masses had connections very dierent from those now obtaining; 
and these turtles were able to become diffused to regions now widely separated by 
deep seas from the original home of the creatures. It erould appear more reasonable 
to suppose that South America had received its original pleurodiran population 
from North America, by the way of some Mesozoic land connection; but it is 
possible that these immigrants reacht that continent from Africa. A considerable 
number of authors, viewing the subject from different positions, have concluded that 
there was, during the Mesozoic era, a land connection between South America and 
Africa, which connection was interrupted about the beginning of the Tertiary. 
The existence of such a bridge would enable us to account for the occurrence of 
some closely related species in Madagascar and South America. These species are 
usually referred to the genus Prdbeneutins but Baur regarded the Madagascar 
species as belonging to the closely related genus Erymnoc helys. Two species of 
Podocnemts are reported from the Middle Eocene beds of the F ayum, Egypt. 
Inasmuch as Pleurodires once occupied a large part of the north temperate zone, 
it is remarkable that they have not been able to maintain themselves there. The 
first and the last that are known to have lived in North America flourisht during 
