§ 59. RETROSPECT. 285 



gypseous shale, and indurated calcareous marl, with sulphur, 

 salt, and gypsum. 



59. Retrospect. — So numerous and varied have been 

 the phenomena presented to our notice, that a compre- 

 hensive retrospect is necessary, in order to obtain a correct 

 idea of the highly interesting deductions resulting from 

 this general survey of the tertiary formations. 



In the newer tertiary, or pliocene, including the mam- 

 malian epoch of the last lecture, the fossil remains in the 

 alluvial deposits afford incontestible proof that the mam- 

 moth, mastodon, hippopotamus, dinotherium, elk, and other 

 colossal animals of extinct species and genera, together with 

 birds, reptiles, and carnivora, inhabited such districts of our 

 continents as were then above the waters : while the older 

 tertiary, or eocene, inclose the bones of land animals, prin- 

 cipally pachyderms, approximating to certain races that 

 now exist in the torrid zone, but which belong to cxrinct 

 genera. The seas and lakes of that remote epoch occupied 

 areas, the greater part of which is now dry land : and rocks 

 and mountains, hills and valleys, streams and rivers, diver- 

 shied the surface of countries which have since been either 

 destroyed, or entirely changed; and whose past existence is 

 only revealed by the deposits that were accumulated in the 

 lakes and deltas, by streams and rivers. The ocean abounded 

 in mollusea, Crustacea, and fishes, of which a large proportion 

 is referable to extinct species. Crocodiles, turtles, birds, and 

 insects, were contemporary with the palaeotheria, and anoplo- 

 theria; and animal organization, however varied in certain 

 types, presented the same general characters as in modern 

 times: the extinction of species and genera being then, as 

 now, in constant activity. The vegetable world also contained 

 the same great divisions ; there were forests of oak, elm, 

 and beech ; of firs, pines, and other coniferous trees ; palms, 

 tree-ferns, and the principal groups of our modern floras ; 

 while the water, both salt and fresh, teemed with the few 



