CONTAINING FLINT IMPLEMENTS, AND ON THE LOESS 
279 
identity with those now living in the same area. There are rarely sufficient modifica- 
tions in size or form to lead us a priori to infer any material differences in the conditions 
under which they lived. Certain species of Pisidium, Cyclas, Limncea , Succinea , Planor- 
bis, Helix , &c., were then, as now, among the most abundant shells. Some varieties, 
such as one of Pisidium fontinale , and that of Helix pulchella , are, I am informed by 
Mr. Jeffkeys, forms more peculiar to the north of Europe. The Hydrobia marginata , 
though not known in northern Europe, ranges high in the subalpine tracts of the Jura 
and Alps. 
But though there is nothing sufficiently specific in the individual species to indicate a 
climate different from that of the present day, there is at the same time nothing to 
require restriction to an identical climate. If, further, we look at the group as a whole, 
we shall find it to have not only a very wide range, but one more in a northern than in 
a southern direction. Of the 36 species found in these high-level gravels, 29 are found 
in the plains or on the hills of Lombardy*, whereas 34 of them range to Sweden and 31 
to Finland; amongst these are the common Succinea putris, S. elegans , Helix hispida , 
H. nemoralis , H. pulchella, Zonites radiatulus, Pupa marginata , Limncea peregra , L. pa- 
lustris, L. truncatula, Planorbis vortex , P. complanatus , P. albus, P. spirorbis , Bytkinia 
tentaculata , Ancylus fluviatilis, Valvata piscinalis, Cyclas cornea , Pisidium amnicum, and 
P. fontinale. Many range further north in Europe, but there is no list of the land and 
freshwater shells of any more northern district so complete as that of Finland f. It is 
known, however, that a great number of these same species are found in Siberia. The 
annual freezing of the rivers, even in less northern latitudes, proves at all events the 
power of these mollusks to endure a great winter cold J. This capability of enduring 
severe cold, and their northern range, show that they could readily have adapted them- 
selves to great changes of climate in the region where they are now found. The general 
absence of southern species is also not without its significance ; for while out of a total 
of 77 Finland species 31 have been found at the few places named in our list (see Ap- 
pendix), only 29 out of the 193 Lombardy species have been met with in these beds. 
Our knowledge of the fossil Mammalia of the high-level gravel-beds is very incom- 
plete. I might, it is true, include those I have reason to believe are of the same age 
and which would furnish us with more complete and positive data — such, for instance, 
as a great number of the cave-deposits ; but, from the circumstances I have before alluded 
to, I deem it best to confine myself to these particular beds and to the localities where 
flint implements have been found. Few of our own high-level gravels contain any 
organic remains at all : in the greater part they are entirely absent. 
* Catalogo dei Molluschi della Lombardia, by A. & G. B. Villa. Milan, 1844 & 1853. 
t Finland Mollusker, af Nordenskiold och Hylander, Helsingfors, 1856. 
+ Picard mentions an instance where some specimens of Limncea auricularia he had placed in a vase, froze 
in the ice, which was exposed to a temperature of — 2°Fahr. When the thaw came and they were released 
they soon recovered and became as active as ever. — Op. cit. p. 278. 
MDCCCLXIV. 
2q 
