84 



I am also inclined to think that we have better means of 

 detecting, from fossil remains, the influences which affect 

 contemporaneous distribution in marine mollusca than can be 

 discerned from among corresponding remains in regard to a 

 terrestrial flora. 



In reading Ljell's description of the lacustrine formations 

 of the Lower Miocene of France, I was much struck wiih 

 their characteristics. If the local names be left out, we 

 might apply his account as an excellent general description 

 of the extensive lacustrine formations of Australia or 

 Tasmania. He remarks : — 



" Lacustrine strata, belonging for the most part to the 

 same miocene system, as Calcaire de la Beauce, are again 

 met with further south in Auvergne, Cental, and Velay. 

 They appear to be monuments of ancient lakes, which, like 

 some of tliose now existing in Switzerland, once occupied the 

 depressions in a mountainous region, and have been each fed 

 by one or more rivers and torrents. 



" The country, wdiere they occur is almost entirely com- 

 posed of granite and different varieties of granite- schist, with 

 here and there a few patches of secondary strata much 

 dislocated, and which suffered great denudation. There are 

 also some vast piles of volcanic matter, the greater part of 

 which is newer than the freshwater strata, and is sometimes 

 seen to rest upon them, while a small part has evidently been 

 of. contemporaneous origin. 



" The study of these regions possess a peculiar interest 

 very distinct from that derived from the investigation, either 

 of the Parisian or English tertiary areas, for vre are presented 

 in Auvergne with the evidence of a series of events, astonish- 

 ing magnitude and grandeur by which the original form and 

 features of the country have been greatly changed, yet never 

 so far obliterated but that they may still, in part at least, 

 be restored to imagination. Great lakes have disappeared, 

 lofty mountains have been formed by the reiterated emission 

 of lava preceded and followed by showers of sand and 

 scoriae, deej) valleys have been subsequently furrowed out 

 through masses of volcanic origin ; at a still later date new 

 lakes have been formed by the damming up of rivers, and 

 more than one assemblage of quadrupeds, birds, plants, 

 eocene, miocene, and pliocene, have followed in succession. 

 Yet the region has preserved from first to last its geographical 

 identity, and we can still recall to our thoughts its external 

 condition and physical structure before these wonderful 

 vicissitudes began, or while a part only of the whole had 

 been completed." 



This remarkable j^icture of the lacustrine formations of 

 the south of France would be a wonderfully faithful 



