GEOGRAPHICAL DISTRIBUTION. 31 
A glance at fig. 9 will show at once the great influence of heat and cold and the 
lack of moisture. In western Europe, warmed by the sea, the turtles are represented 
by a species which ranges nearly as far north as St. Petersburg; while in Central 
Asia none is known to occur north of Turkestan and the Himalaya Mountains. 
The southern portion of Arabia and the greater portion of the Sahara Desert are 
without turtles, on account of the dryness of the climate. In North America the 
high and cold range of the Rocky Mountains supports no chelonian life. On account 
of its dryness, the western coast of South America has no turtles; and the southern 
extremity of the continent none, on account of its coldness. So much can we say 
with regard to turtles in general; but when we come to study the different groups 
we shall find that they are often absent from regions where the conditions appear 
to be wholly favorable for their existence. 
EQUATOR 
Fic. 9.—Map showing geographical distribution of living turtles, excepting those strictly marine. 
Occupied areas ruled with parallel lines, except some Snail islands: which are in solid black. 
Fig. 10 is intended to display the distribution of the Cryptodira. It is seen to 
differ from the previous map principally in that it shows that Australia possesses no 
representatives of the superfamily. 
ae 
Fic. 10.—Map showing geographical distribution of the Cryptodira. 
The absence of Cryptodira from Australia is evidence that that region has for 
many geological ages been cut off from the regions to the north of it. It appears 
certain that had the turtles of this superfamily once gained access to this region they 
would have flourisht there. In numbers the Cryptodira exceed today all other 
