96 MR. G. NEVILL ON THE [Feb. 1 7, 



of this immense deposit, one occasionally comes across some large 

 boulder, around and below whicli I found these subfossil shells, 

 often in great profusion, sometimes iucrusted in the rock itself, but 

 generally fortunately preserved in the soft red earth which fills the 

 crevasses of these enormous blocks of stone, in a condition as fresh 

 and perfect as on the day they were buried. 



There can, I think, be only one explanation of the really wonderful 

 condition in which they are preserved : most undoubtedly the moUusks 

 were at the time for the most part alive, actually Uving on the exact 

 spots where they are still to be found. There they must have 

 been suddenly buried as they lived, in situ, by the large deposits 

 of this old Conglomerate, which one still finds heaped above them, 

 of a thickness here of some 10 to 30 feet at least (oftentimes more), 

 perhaps brought down by some enormous glacier from the high neigh- 

 bouring Alps, by the St.-Louis gorge, which latter even may have 

 been excavated as one finds it at present by this same action. 



I ought to add that these subfossils are but rarely to be found on 

 the surface itself : to discover them one has to dislodge the larger 

 stones and excavate the soil. 



Dr. J. Henry Bennet describes, in a most lucid way, this 

 "Pleiocene conglomerate," in his interesting work 'Winter and 

 Spring on the shores of the Mediterranean.' At page 39 he gives an 

 account of the Geology of Menton, as also of the discovery of the 

 bones of extinct wild beasts in these caves ; he there estimates the 

 thickness of this " conglomerate " in the neighbourhood at from 

 COO to 800 feet. At page 45 he speaks of the extreme probability 

 of glacial action ; but he is of the opinion of Dr. Niepce, of Nice, 

 that it was formed under the sea, before the Glacial period, and 

 afterwards thrown up in its present position. The first view is 

 doubtless correct ; but the last certainly can not have been the case 

 in the instances of which I am treating. These mollusks, interred 

 immediately under this conglomerate, undoubtedly have never been 

 subjected, in the most remote manner even, to the action of the sea. 



I am quite of the opinion of Monsieur Bourguignat, that this 

 conglomerate was formed very shortly after the Glacial period : 

 the characters of these mollusks prove the climate to have been 

 then very cold at the present sea-level ; so the temperature must 

 have been perfectly boreal on the summits of the neighbouring 

 mountains. This would appear to be also the opinion of Prof. 

 Issel(AppuntiPaleont. Ann. Mus. Civ. Genova, vol.xiv. p. 11) ; he 

 describes a similar deposit at Ventimiglia containing the bones of an 

 extinct species of Elephant as belonging " al periodo Quaternario 

 postglaciale." 



The following deposits or beds {A to D) of this Conglomerate, 

 without doubt of one and the same age, contain these subfossil 

 mollusks : — 



A. This was the only one of these deposits we could discover in 

 France itself, all the others being in Italy : it is situated a few yards 

 only from the frontier, a stone's throw from the " Pout St. Louis," 

 about 50 metres above the sea, I should estimate; aspect nearly 



