Ch.XXIL] EOCKNE 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. 



