CONTAINING FLINT IMPLEMENTS, AND ON THE LOESS. 
283 
as the hill of St. Gilles with respect to Menchecourt — there we might expect a quieter 
deposition of sedimentary matter ; and this we find to be the case at the latter place. 
These causes, as in all rivers of the present day subject to heavy periodical floods, 
must have operated very generally during this quaternary period, and have rendered 
the remains of freshwater mollusca in these fluviatile deposits the exception and not the 
rule. As a proof of this, I may remark that I am not aware that land and freshwater 
shells had been noticed in the lower gravels of the Seine valley until I discovered the 
few species mentioned at page 261*. Neither the valley of the Lark nor the valley of 
the Waveney have yet yielded any. In the valley of the Ouse they are more common, 
though still comparatively scarce. 
As with the pulmoniferous Testacea of the high-level gravels, although there is 
nothing in the individual species found in the low-level series to give a definite clue to 
the character of the climate of the period, still the group maintains its northern ten- 
dencies, there being, out of a total of 52 species, 42 now living in Sweden and 37 in 
Finland (or nearly one-half of the Finnish species), whereas only one-fifth, or 38, of the 
Lombardy species occur in these quaternary beds. The marine shells are also common 
temperate and cold-climate species. The Littorina squalida alone slightly weighs the 
balance in a more northern direction ; but, on the other side, we have to notice the 
introduction of a few more southern land and freshwater species, such as the TJnio 
littoralis, of the Helix cajperata , Pomatias obscurus, and the abundance of Cyclostoma 
elegans , which may be taken as some evidence of a more genial climate than that of the 
period preceding it. The profusion also of the land and freshwater testacea, and the 
greater abundance and variety of animal life, support this latter view. The great bulk 
of the species, both of Mollusca and Mammalia, being common to both levels of gravel, 
we may presume that no very important change in the mean temperature then took 
place, and that any transition was gradual, although it is possible that the winter 
climate of the one period may have differed to some extent from that of the other. 
The following species of Mammalia have been found in these low-level gravels. I 
am indebted to Dr. Falconer for the determination of all the Bedford specimens, and 
to M. Lartet for the Paris list. The species from the Somme valley are the same as 
given in my former paper. 
This list, although more complete than that of the other series, must be taken only as 
a very partial representation of the fossil Mammalia of the period. There are other 
localities beyond our inquiry which, as with the Mollusca, would afford a larger and 
more varied list, like, for example, the valley of the Thames f; but, as I purpose to 
show their synchronism at length, I consider it better in this more special inquiry to 
confine myself to the above species. There are enough, independently of other loca- 
lities, for the general argument, which, so far as regards the Elephant and Rhinoceros, 
follows the same line as that relating to the high-level gravels. 
* Besides these (ante, p. 261) I found in a marl in a higher level and corresponding with the Loess, Helix 
hispida, H. pulchella, H. nemoralis, Pvpa marginata, Succinea putris, Avion ater, and Bythinia tentaculata. 
f And the valley of the Wiley at Salisbury (Dr. Blackmobe’s remarkable collection). — March 1864. 
