324 
THE GEOLOGIST. 
possibly have withstood any transfer, are such as are associated with similar 
remains elsewhere in France and in England, where we have no reason to doubt 
the contemporaneity of the two sets of organisms. 5. At St. Acheul part of 
the lower jaw with the teeth, and considerable lengths (four and five feet) of 
the tusks of E. primigenius have been found. At. Meuchecourt the bones of 
the leg, lying in their natural position, and nearly the whole skeleton of a 
Rhinoceros, were found entire, — the first being an improbable, and the second 
an impossible contingency, had the remains of the animal been washed out or 
removed from some older deposit. 6. Lastlv, the extinct mammalia are of 
species which occur, both in England and France, only in the latest geological 
deposits, whereas if these remains were here extraneous, we should expect to 
find some species peculiar to deposits of anterior date. 
Mr. Prestwich continues, in his geological considerations of the question : — 
" 1 should not wish, until after fuller study of the district, to enter on the 
question regarding the mode of formation of the above-described deposits of 
Abbeville and Amiens, beyond pointing out, that, at the former place, the 
evidence of the lower beds of Menchecourt having been deposited partly in 
fresh water, and partly in salt or brackish water, seems sufficiently clear and 
distinct. Apart from the latter condition, the St. Acheul sands {n), as well as 
the lower gravel {d) containing the flint-implements, may also be attributed to 
a like accumulation under fresh water. The upper beds {b) in both cases are, 
I believe, of entirely different origin, and belong to a class of phenomena of far 
wider extent and generality. At the same time, while postponing the more 
theoretical questions, the one concerning the relative age of the deposits can, 
to a certain extent, be considered independently upon the evidence of the 
organic remains and of correlation ; and certaia general conclusions may be 
ventured upon. 
" It is probable that subsequently to that phase of the Glacial period marked 
by the Boulder clay, the area of dry land became more extended, and on it there 
lived the Elephas primigenius and E. antiqnus. Rhinoceros tichorinus, Hycena 
spelaa, with species of Beer, Horse, and other animals, mostly of extinct, but 
some of species not to be distinguished from the recent ; wliilst the waters of 
both sea and land were tenanted almost exclusively by shells of recent species 
still common in this and adjacent countries. The remains of this old surface 
we find in deposits, which everywhere contain a similar group of organic 
remains, and occur mostly in old valleys or at moderate elevations. They are 
never overlaid by other fossiliferous deposits, and I believe them all to belong 
to a state of things which ini'nediately preceded the present order. One fea- 
ture of these deposits is, that although closely related to the present configura- 
tion of the surface, yet they are always more or less independent of it. They 
are often near present lines of drainage, yet could not, as a whole, possibly 
have been formed under their operation. The deposits described in the pre- 
ceding pages are, there is little doubt, of this age, and they have many ana- 
logues in France and England. The Meuchecourt beds bear a very close resem- 
blance (the marine characters apart) to those of Fisherton, near Salisbury. 
The deposit at St. Acheul is like, in many respects, the Ilford and the Brent- 
ford beds, whilst that of Moulin Quignon and St. GiUes closely resembles the 
gravel;beds at Croydon, Wandsworth Common, and some other places n«ar 
London. 
" The gravels of Moulin Quignon and St. Acheul are placed respectively 
eighty-eight and eighty-niae feet above the valley of the Somme, are not com- 
manded by any higher ground immediately adjacent, and are out of reach of all 
running water, or of any possible interference from agents at present in action. 
At Menchecourt and St. Roche, on the contrary, the beds are placed against 
the side of the chalk hills, and slope from a height of about sixty feet down to 
