LIFE ON THE EARTH. 149 



bounds ; as we may perhaps suppose the marine 

 Turtles and Saurians of the Mesozoic and Cainozoic 

 periods occasionally to have done. In migrations of 

 this kind it is difficult to assign the limits ; indivi- 

 duals may arrive and live, where the race would soon 

 perish in the struggle with unfavourable natural con- 

 ditions. 



In the earlier Tertiary periods, the excessive pre- 

 dominance of Pachydermatous Genera, allied to Tapir, 

 Rhinoceros, Hippopotamus, Elephas, and the occur- 

 rence of their remains in old lakes and marshes, &c. 

 seem to require the hypothesis of their having lived 

 through long ages in the latitudes of Paris, the 

 Rhine-land, and England. Granting that they in- 

 dicate a warmer climate then prevailing, we may 

 confirm it by the remains of Serpents and Monkeys 

 found in the London clay at Kyson near Ipswich 1 . 

 But in the later Tertiary epochs, the frequent mixture 

 of Rhinoceros and Hippopotamus and Elephant with 

 Horse, Ox, Deer, Wolf, Bear and other quadrupeds, 

 whose relatives are found in various climates, and are 

 known by experience to prosper in the climates now 

 prevalent where their remains occur, renders inferences 

 as to climate from them too vague and indecisive to 

 be trusted. With these mixed land quadrupeds lie 

 in several situations, in old Pleistocene lakes, shells 

 1 Owen in British Fossil Mammalia. 



