vi] DISTRIBUTION OF SELECTED GROUPS 99 



world, of which the present 20 species are the scanty 

 remainder. Long-snouted gavials occur in the Upper 

 Cretaceous of New Jersey and Europe, in the Mio- 

 cene of Europe, now restricted mainly to the Ganges 

 and Malay Islands. Crocodiles have lived in Europe 

 since the Upper Chalk, and many kinds flourished 

 there, and in North America during Tertiary times ; 

 now in Africa, India to North Australia, and in 

 tropical America, including the West Indies. Alli- 

 gators and caimans, formerly also in England, are 

 now almost entirely American, but one species lives 

 in the Yang-tse-kiang as a reminder of the probable 

 Eurasian origin of the whole group. 



TORTOISES. 



The marine turtles are found in all the warm to 

 temperate seas. Most of the groups of the land 

 and freshwater tortoises were evolved before the 

 Tertiary period, and attained a perhaps world-wide 

 range, so that the present distribution of the 200 

 species represents only the remainder of a sub-class 

 which has had its day. 



Pleurodira, or water-tortoises, which tuck away 

 their long neck sideways, were plentiful in Mesozoic 

 times in Europe, India and North America ; now re- 

 stricted to Africa and Madagascar, South America 

 and Australia. On the latter continent they are the 



72 



