Ch. XXIV.] OF MOUNTAIN-CHAINS. 343 



western end of the Pyrenees, near Bayonne, are certainly of 

 the Miocene period. 



Such, then, being the age of the strata, and granting even 

 that the movement occurred after the period of the white 

 chalk, and before the beginning of the Miocene era, there still 

 remains ample scope for conjecture as to the date of the event. 

 For the upheaving of the Pyrenees may have been going on 

 when the animals of the Maestricht beds flourished, or during 

 the indefinite ages which may have elapsed between their ex- 

 tinction and the introduction of the Eocene tribes, or during 

 the Eocene epoch, or between that and the Miocene. Or the 

 rise may have been going on continuously throughout several 

 or all of these periods. 



But this is not all ; we must include within the possible space 

 of time wherein the convulsions may have happened, part of the 

 epochs both of the chalk and of the Miocene species. We have 

 stated, that the newer Pliocene beds in Sicily have been raised 

 during the newer Pliocene epoch, partly, perhaps, in the 

 Recent, but this latter supposition will lend equal support to 

 our present argument. Now, it is evident that the greater part 

 of the species of testacea which pre-existed in the Mediterranean 

 have survived the elevation of the newer Pliocene beds in 

 Sicily, and in the same manner there is no reason to conclude 

 that the rise of the chalk in the Pyrenees exterminated the 

 animals which lived in the sea wherein the chalk was formed. 

 In that case, a series of convulsions may not only have begun, 

 but may even have been completed before the era when the 

 Maestricht beds originated. 



In like manner the sea may have been inhabited by Miocene 

 testacea for ages before the deposition of those particular 

 Miocene strata which occur at the foot of the Pyrenees, and 

 the disturbing forces may have operated in the Miocene period, 



from the newest secondary beds on the flanks of the Pyrenees, near Bayonne, were 

 examined by M. Deshayes, and found identical with species of the chalk near 

 Paris. 



