THE EUBOPEAN SEAS. 



251 



phenomena of pure geology require and imply, 

 they are brief comparatively with those during 

 which a definite marine fauna has maintained its 

 existence. It will be seen in the sequel how great 

 are the physical changes which have taken place in 

 the northern hemisphere, since a large proportion 

 of our existing Testacea have occupied the Northern 

 Atlantic. 



The fauna of the European seas dates back its 

 origin, or first appearance, to times which (on the 

 scale of the geologist) follow next after the Num- 

 mulitic period (Eocene). So far as European seas 

 are concerned, they do not contain a single species 

 in common with the forms of the nummulitic 

 group. The earliest records of the occupation of 

 the Atlantic by any existing forms are certain old 

 sea-beds, which are scattered at intervals over some 

 of the western departments of France, extending 

 inland along the valley of the Loire, as far eastward 

 as beyond Blois, to be met with in some of its 

 branches northwards — an old arm of the Atlantic, 

 with dimensions nearly equal to those of our Eng- 

 lish Channel, long since laid dry. These old sea- 

 beds are the " Faluns of Touraine." 



Lower down to the south, from the Island of 

 Oleron, across to the Adour, was another great 

 indent of the Atlantic — an eastern extension of the 

 Bay of Biscay. Over this once depressed area 

 there are sea-beds which contain an assemblage like 



