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. Menchecourt 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 : — 

 " I 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 (c), 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 f a certain extent, be considered independently upon the evidence of the 

 organic remains and of correlation ; and certain 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 primigetiius and E. antiquus, Rhinoceros tichorinns, Hy&na 

 spelaa, with species of Beer, Horse, and other animals, mostly of extinct, but 

 some of species not to be distinguished from the recent ; whilst 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 immediately 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 Menchecourt beds bear a very close resem- 

 blance (the marine characters apart) to those of Eisherton, 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. Gilles closely resembles the 

 gravel-beds at Croydon, Wandsworth Common, and some other places near 

 London. 



"The gravels of Moulin Quignon and St. Acheul are placed respectively 

 eighty-eight and eighty-nine 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 



