6 GEOLOGICAL MEMOIRS. 



The fossils that favoured this opinion are, — 



The Ammonites suhfascicularis, D'Orb. ; found by Sig. Prof. Cav. 

 Sismonda in several localities in the county, and by me in the Valley 

 of S. Andrea, together with A. tortisulcatus, D'Orb. This species 

 was afterwards referred by D'Orbigny to the Jurassic series. 



Ammonites virgatus ; cited by Sismonda with some doubt*. 



An Aptychus ; determined by M. Bellardi as the A. Bidayi (Co- 

 quand) ; but in this fossil M. Bellardi afterwards found some differ- 

 ences from the true A. Bidayi in the number and direction of the 

 costee, on comparing it with a well-preserved individual of that 

 species. 



Ammonite^ Ixion, Belemnites dilatatuSy B. pistilliformisy and B. 

 subfusiformis ; these were really found in the greenish neocomian 

 sandstone, which some would unite with this limestone, which occurs 

 in the same localities. 



General inferences. — Reasoning upon what I have here brought 

 forward, it appears to me possible to arrive at the following conclu- 

 sions : — 



1 . That the macigno in the Maritime Alps is always superior to the 

 nummulitic strata. 



2. That the nummulitic terrain in the different localities of the 

 Maritime Alps above cited is identical in age and character, if not in 

 development. 



3. That of the fossils which it contains, the greater part are Eocene, 

 some are peculiar to it, and some are Cretaceous. 



4. That it is perfectly distinct in its characters from the cretaceous 

 strata on which it reposes, — sometimes unconformably ; and conse- 

 quently that it cannot be classed with them. 



5. That the Hippurite-limestone with Nummulites may sometimes 

 possibly be in contact with the nummulitic terrain in the South of 

 France, and in other places, but that the two groups have no cha- 

 racter in common, except the presence of the genus Nummulites^ — 

 and not the species, as was supposed by Prof. Pilla. 



6. That, if a few fossils be sufficient to characterize a deposit, a 

 larger number are more decisive ; whence it follows that, taking into 

 account the numerical proportion of species, the Alpine nummulitic 

 terrain should be referred to the eocene and not to the cretaceous 

 period, very few fossils referable to the latter having as yet been 

 discovered in the localities above-mentioned, and some even of these 

 are doubtful. 



7. That the Alpine nummulitic terrain ought from its characters 

 and fossils to be classed as intermediate between the cretaceous and 

 the supracretaceous, as MM. Pilla and Leymerie think ; or at least it 

 should be united with the tertiary series as a lower member, but 

 quite detached from the chalk, as M. Michelin has suggested. 



8. That the marly limestone with Inoceramii Am. Mantelliy Am. 



* Notizie e schiarimenti suUa costituzione delle Alpi piemontesi del Prof. Sis- 

 monda, p. 89. 



