114 Considerations on determining 



more exact than I had been able to make, — to regard them 

 as belonging to the most recent of the tertiary formations. — 

 He points out there, indeed, 50 per cent, of species analogous 

 to those still existing, for the most part, in the Mediterranean; 

 and he connects them with the strata of Sicily, and the sub- 

 appennine hills, in which M. Deshayes indicates the same 

 proportions, but which he distinguishes from the faluns, as 

 forming a more recent tertiary stage. 



While the researches and exact determinations of M. Du- 

 jardin tend to lessen the antiquity of the deposit of the faluns 

 of the Loire, an examination of the fossil shells of the crag of 

 England, rendered easier by the assemblage of a larger num- 

 ber of species than M. Deshayes had been acquainted with, 

 led to a diametrically opposite result. A very numerous col- 

 lection of these shells, studied about a year since, in London, 

 by Dr. Beck, of Copenhagen, curator of the museum belong- 

 ing to the Prince Royal of Denmark, presented to him nume- 

 rical results, very different from those previously established 

 by M. Deshayes, and adopted by Mr. Lyell, in support of the 

 classification of the crag in the upper division of the tertiary 

 strata. Instead of recognising there 50 per cent, analogous 

 to the living species of the German ocean, Dr. Beck considers 

 almost all the fossil species of the crag which he has exa- 

 mined, to the number of four hundred and fifty, as distinct 

 from any known existing species; though he finds among 

 them in general, more resemblance to those of the north seas 

 than to any others* Mr. G. B. Sowerby has joined in the 

 same opinion, as to the almost total absence of analogous 

 species. M. Agassiz having examined the remains of fishes, 

 and M. Milne Edwards those of Polypi, which are very nu- 

 merous in this deposit, have found no species analogous to re- 

 cent ones. In support of these considerations, which tend to 

 heighten the antiquity of the English crag, great stress has 

 recently been laid on the presence, in this deposit, of the 

 teeth of the Mastodon, which are also found in the faluns, an 

 argument of which I availed myself, in favor of the contem- 

 poraneous origin of the two deposits. Upon these determi- 

 nations, many English geologists have not hesitated to bring 

 down the crag into the middle tertiary formation ; whilst the 

 computations of M. Dujardin would reduce the age of the fa- 

 luns to a much more recent period ; a result, the inverse of 

 that arrived at by M. Deshayes and Mr. Lyell. 



* Proceedings of the Geological Society of London, Vol. II. No. 44 ; 

 address of Mr. Lyell on the progress of the Geological Society of London, 

 in 1835.— Read on the 19th of February, 1836. 



