SAVI ON THE MONTI PISANI. 9^ 



present therefore he determines to class the upper secondary for- 

 mations of Tuscany, the macigno as well as the alberese, amongst 

 the cretaceous formations, and consequently as belonging tO-^-lrfee-^ 

 upper chalk. ' r/^:,tr<,jw 



From the absence of all interruption in the stratification, the 

 author concludes that the secondary supra-jurassic beds of Tuscany 

 must contain the equivalents of all the members of the chalk of the 

 N.W. of Europe ; but owing to the scarcity, bad preservation, or even 

 total absence of organic remains in many beds, it is extremely difficult, 

 if not absolutely impossible, to ascertain the exact limits of the dif- 

 ferent portions corresponding with those of the chalk of the north. 

 Nevertheless it may be considered that the beds comprised between 

 the nummulitic lumachella, the variegated limestone, and the argil- 

 laceous marly schists inclusive, generally belong to the upper chalk, 

 and then the underlying series M'ould represent the lower chalk 

 and the Neocomian. 



Having thus completed the examination of these formations, a 

 careful consideration of all the preceding phsenomena leads our 

 author to the following conclusions (p. 65): — * '"^ 



" 1. That the secondary formations of Tuscany were all depo- 

 sited at the bottom of one ocean, in regular and uninterrupted suc- 

 cession. 



" 2. That many of the living beings which inhabited the sea 

 by which this country was submerged, during the deposition of the 

 upper Jurassic beds, were not the same as those which at the same 

 time inhabited the more northern seas ; and that probably when 

 some of these species had disappeared in the N. and N.W., they 

 still continued to exist in the sea of the Italian regions. 



" 3. That the sea which covered a great portion of Italy and 

 of the Alps during the period of the deposit of the chalk, existed 

 under circumstances different from those under which the sea, 

 which at the same time covered the west and north-west of Europe, 

 and even the north of Italy, existed." ' 



These conclusions are supported by various arguments, amongst 

 which the author says respecting the second : — " The above consi- 

 derations lead to a consequence which it is difficult to reconcile with 

 the principles recently adopted, viz. to consider zoological cha- 

 racters as not always sufficient to determine the age of the Jurassic 

 beds. But besides that this opinion is so powerfully confirmed by 

 the above-mentioned facts, it is also supported by the considerations 

 respecting the actual distribution of animals now living on the earth, 

 and the fact of our knowing that some species have disappeared ; 

 and I am persuaded, that when we shall be better acquainted both 

 with the numbers and the species of the fossils peculiar to the va- 

 rious formations of the southern regions, and when the synchronism 

 of these formations with those of the north shall be perfectly known, 

 not only will all uncertainties vanish, but perhaps we shall be able 

 to lay down with accuracy the laws which have determined the 

 succession of organic life at different periods and in different por- 

 tions of the globe, and consequently be enabled to fix the rules by 



