CHAP. XI.] HANTONIA1C PERIOD. 227 



sented in the London Clay. Their aspect is completely 

 different, and though separated geologically by but a short 

 interval of time, hardly any species are common to both, 

 while the lithological characters of the formation are widely 

 and persistently dissimilar. If we examine, on the other 

 hand, the terrestrial fauna and flora of these and the 

 intervening strata, we see that no increase of temperature 

 or change had taken place in the climate, and that the land 

 was still inhabited by similar groups of reptiles and plants. 

 It is, therefore, plain that the sea alone had changed, and 

 become much warmer, for depressions had enabled the 

 southern sea, then occupying part of France, to advance 

 and to overlap to a small extent the older deposits." 



Let us now turn to France and learn how this southern 

 sea came to reach so far northward. Professor Prestwich 

 and Mr. Gardner agree in thinking that the northern sea 

 of Lower Eocene times lay to the east and north-east of 

 our islands, and that the greater part of northern and 

 central France was land, this land being continuous across 

 the space between Brittany and Cornwall ; so that the 

 northern sea was entirely cut off from communication with 

 the warmer seas of more southern regions. The Lower 

 Eocenes of the Paris basin were formed in shallow bays 

 and lagoons on the northern border of this land, and their 

 fauna and flora are consequently those of the northern 

 province. 



To the south of this Eocene France lay a wide and deep 

 sea which covered the greater part of southern Europe, 

 spread over the northern borders of Africa, and extended 

 far into the western part of Asia ; this sea was, in fact, a 

 greater Mediterranean, and in it were formed the Nummu- 

 litic limestones which occupy such large areas in the 

 regions above mentioned. 



From the superposition of marine limestones upon the 

 1 <' Proc. Geol. Assoc.," vol. vi. pp. 95, 96. 



