314 



THE GEOLOGIST. 



to both, although some are more common in the lower beds, 

 to which they appear specially to belong {Am. denarius, cris- 

 tatusj, and the others are more peculiar to the upper beds, 

 where they are much more numerous {A. mammillaris, Beau- 

 danti, Dupinianus). 



I have already stated that no species of the Neocomien 

 formation has been found hitherto, among the species of 

 the gault. This is also the case as regards the latter, which 

 I have never found in the beds of the Neocomien. But in 

 the group of the Chloritic chalk, I have noticed three un- 

 doubted examples, of the species of the Gault, A. latidorsa- 

 tus, Mayorianus inflatus. The first is found with the spe- 

 cies of the chloritic chalk, at Cassis (Bouches du Rhone), 

 and at Cape la Heve, near Havre (Seine- Inferieure) ; the 

 second, also at Cassis and at Vergons (Basses Alpes), and 

 the third at Montblainville (Meuse). There are, then, in 

 the gault, three species amongst the upper ones only, which 

 are sometimes found amongst the Ammonites of a higher 

 group. I shall return to this subject when endeavouring 

 to explain the cause of this accidental mixture ; I hope, not- 

 withstanding, to demonstrate equally well, that all the spe- 

 cies are characteristic of the group to which they belong. 



3rd. Group. — Chloritic chalky or upper Greensand, 



The 27 species of Ammonites of the Chloritic and tufa- 

 ceous chalk, or upper green sand, all belong to the lower 

 beds ; the upper beds, or the white chalk, do not contain 

 any Ammonites. Nevertheless, in the lower portion of the 

 chalk, there are species which are always found in the 

 lowest beds, and others in the upper ones. The following 

 are the species : 



AMMONITES. 



AMMONITES. 



Beaumontianus, d'Orb. 

 Bravaisianus, d'Orb, 

 Carolinus, d'Orb, 



Catillus, Sow. 

 Deverianus, d' Orb. 

 FalcatuSy MantelL 



