Ch.XXII.] 
EOCliNE ALLUVIUMS. 
317 
plants of Sheppey ; and the shores of those islands may have 
been frequented, during the ovipositing season, by the turtles 
and crocodiles, of which the teeth and skeletons are imbedded 
in the London clay *. 
Eocene alluviums. — 'The river which produced that body of 
water in which the fresh-water strata of Hampshire originated, 
must have drained some contiguous lands which may have 
emerged during the Eocene period. On these lands we may 
suppose the Paleothere, Anoplothere, and Moschus of Binstead 
to have lived. The discovery of the two former genera, asso- 
ciated as they are with well-known Eocene species of testacea, 
is most interesting. It shows that in England, or rather on 
the space now occupied by part of our island, as well as in the 
Paris basin, Auvergne, Cantal, and Velay, there were mam- 
malia of a peculiar type during the Eocene period. Yet we 
have never found a single fragment of the bones of any of these 
quadrupeds in our alluviums or cave breccias. In these 
formations we find the bones of the mastodon and mammoth, 
of the rhinoceros, hippopotamus, lion, hyaena, bear, and other 
quadrupeds, all of extinct species. They are accompanied by 
recent fresh-water shells, or by the marine fossils of the crag, 
and evidently belong to an epoch posterior to the Eocene. 
Where, then, are the terrestrial alluviums of that surface which 
was inhabited by the Paleothere and its congeners ? Have the 
remains which were buried at so remote a period decomposed, 
so that they no longer afford any zoological characters which 
might enable us to distinguish the Eocene from more modern 
alluviums ? 
It seems clear that a peculiar and rare combination of favour- 
able circumstances is required to preserve mammiferous or 
other remains in terrestrial alluviums in sufficient quantity to 
afford the geologist the means of assigning the date of such 
deposits. For this reason we are scarcely able, at present, to 
form any conjecture as to the relative ages of the numerous 
* We have introduced these islands into the map of Europe, in the 2nd volume, 
which may be supposed to relate to the commencement of the Eocene period. 
