AMMONITES — ZOOLOGICAL, ETC. 



333 



facts to refer to, and which is entirely attributable to the care 

 with which he observed and recorded, what his quick perception 

 in the first instance discovered in the materials of the globe, 

 and which his careful comparisons rendered subsequently- 

 available. 



THE Editor. 



Ammonites Zoologically and Geologically considered, 



(Continued from p. 327.) 



CHAPTER III. 



Geologico- Geographical considerations. 



In the two preceding chapters, we have considered the 

 zoological characters of the species of Ammonites, and their 

 distribution according to the several formations and the 

 division of each formation ; at present, it is my intention to 

 consider the whole series of forms, according to their geo- 

 graphical distribution in the bosom of the basins which con- 

 stituted the seas of the Cretaceous period, or the different 

 gulfs of those seas, which appear to have had faunas more 

 or less distinct from each other, at contemporaneous periods. 

 The considerations into which I have entered regarding the 

 Acetabuliform Cephalopodes of the present period (1), prove 

 that independently of species common to different maritime 

 basins, there are, at the present time, in each sea, a certain 

 number of species peculiar to each of them. Let us endea- 

 vour, by collecting all the facts, to ascertain whether such 

 was not also the case in the ancient seas. 



In order to proceed methodically, I shall pass the different 

 geological groups successively in review, and compare with 



(1) Annales des Sciences Naturelles, July, 1841. 



2 A 2 



