PHYSICS AND NATURAL HISTORY OF GENEVA. 243 



are to be found in the physical nature of the deposit and in the sub- 

 marine character of the soil. 



Professor Pictet on this occasion submitted to the Society some 

 general observations on the association, in the same locality, of the 

 fossils pertaining to different formations, an association which he 

 thinks may be explained by three different causes: 1st, by the fact 

 that the relics of dead animals belonging to one epoch might be pre- 

 served for a certain time in the waters containing the living animals 

 of the succeeding period — a case which would be very rare; 2d, by 

 the fact that some robust species, that is to say, very abundant in one 

 stratum, have survived the cataclysm which had occasioned the 

 destruction of the general fauna, and reappear in small numbers in 

 the succeeding fauna; 3d, by the fact, finally, that one portion of 

 the sea has undergone changes less decided than others, and that in 

 a gulf, for instance, we find the fossils of two different epochs 

 associated, while elsewhere the two faunas remain perfectly distinct. 



We have passed, almost without perceiving it, from geology to 

 palaeontology, sciences which in truth are now inseparable; and here 

 M. Pictet must be again cited for remarks submitted to the Society 

 on a communication by M. de Saussure respecting the discovery of 

 fossil bones of domestic animals in the environs of Charleston. These 

 bones pertain only to the* postpliocene formation, of which the fauna 

 is composed: 1st, of extinct animals; 2d, of animals not living at this 

 time in South Carolina, but still existing in other parts of America; 

 3d, of species still living in the country. After having shown that 

 this formation, in a paheontological point of view, presents the same 

 character as the correspondent formations of Europe, and having 

 discussed different hypotheses to explain the presence of the fossil 

 bones of domestic animals, M. Pictet seems disposed to believe that 

 there has been simply an accidental mixture of recent bones with 

 postpliocene remains. 



Besides the communications just noticed, M. Pictet read before the 

 Society a memoir, in the preparation of which M. Campiche, of Ste. 

 Croix, was associated, on the nautili, and more especially cretaceous 

 nautili. After reciting that the nautili are one of the kinds, not many 

 in number, which are met with in all geological epochs, M. Pictet has 

 shown that their distinctive characters may be classed under four 

 heads; and though he has essentially occupied himself, in that part 

 of his investigation prosecuted in common with M. Campiche, with 

 the nautili of the Jura, he and his associate have compared a very 

 great number taken from all formations and all countries, with the 

 view of arriving at a decision as regards the order of succession in 

 their forms. They have ascertained that the definite species of the 

 same epoch are exactly alike in all countries, and that this is also the 

 case with the types imperfectly defined, so that it becomes an imme- 

 diately accessory question whether these types are species or varie- 

 ties. This special question recalling M. Pictet to some general con- 

 siderations on the subject, he is led to regard the three following laws 

 as being at the basis of all palaeontology: 1st, every species has had 

 in its palaeontological development a limited duration; 2d, the co- 







