GEOGRAPHICAL DISTRIBUTION. 



3 1 



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. 



FIG. 9. Map showing geographical distribution of living turtles, excepting those strictly marine. 

 Occupied areas ruled with parallel lines, except some small 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. 



FIG. 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 



