226 THE WONDERS OF GEOLOGY. Lect. III. 



mice, rat, and beaver ; and the large extinct form of the 

 latter, that occurs in the mammoth drift of Russia (the 

 Trogontherium, see ante, p. 154) ; a portion of the jaw of 

 an opossum, and bones of unknown species of water-mole, 

 deer, roebuck, monkey, and bat.* 



The passage of the mammaliferous crag into the alluvium, 

 is in many places so imperceptible, that no line of chrono- 

 logical separation can be drawn ; and our previous remarks 

 on the deposits of the valley of the Thames, render farther 

 comment unnecessary. 



18. Eocene, or lower tertiary deposits. — I now 

 proceed to the consideration of the Eocene, or those tertiary 

 strata which are of the highest antiquity, and occupy basins 

 or depressions of the chalk, where that formation constitutes 

 the fundamental rock of the country. Every step of our 

 progress will now be replete with increased interest, and the 

 relics of new and extraordinary forms of being will appear 

 before us. I shall pass rapidly over the stratigraphical 

 character of these rocks, that our attention may be more fully 

 directed to the organic remains which they inclose. 



I will first describe the geographical distribution and 

 general characters of a few of the principal groups, and 

 the more remarkable fossil animals and plants ; and then 

 survey those regions of central France, of the Rhine, and 

 of South America, which have been the scenes of active 

 volcanoes during the tertiary epoch. 



It may be regarded as a singular coincidence, that the 

 capitals of Great Britain and France are located on strata 

 of the same geological age. Paris is situated on a vast 

 alternation of marine and fresh-water beds, lying in a de- 

 pression of the chalk ; the latter forming the boundary of 

 the area in which the city is placed. London also is built 



* At Ostend, near Bacton, Norfolk ; see Medals of Creation, vol. ii. 

 pp. 859 — 867. Professor Owen has figured and described the most 

 important of these relics in " British Fossil Mammalia." 



