THE STRUCTURE AND CLASSIFICATION OF ROCKS. 



TEIITIARY PERIOD. 



639 



Skeleton of the Anoplotherium 



Skeleton of the Megatherium. 



Mammalia : 1 Eocene period, 50 species. Paleotherium, 

 Anoplotherium, Lophiodon, Anthracotherium, Che- 

 roptamus (allied to the hog), Adapis (resembling 

 the hedgehog). Carnivora .- Bat, Canis (Wolf and 

 Fox), Coatis, Racoon, Genette, Dormouse, Squirrel. 

 Reptiles : Serpents. 



Birds: Buzzard, Owl, Quail, Woodcock, Sea-lark, Cur- 

 lew, Pelican, Albatross, Vulture. Reptiles : Fresh- 

 water Tortoises. Fishes . Seven extinct species of 

 extinct genera. 



2. Miocene Period: Ape, Dinotherium, Tapir, Cha- 

 licotherium, Rhinoceros, Tetracaulodon, Hippothe- 

 rium, Sus, Felis, Machairodus, Gulo, Agnotherium, 

 Mastodon, Hippopotamus, Hcrse. 



3. Pliocene Period : Elephant, Ox, Deer, Dolphin, 

 Seal, Walrus, Lamantin, Megalonyx, Megatherium, ; 

 Glyptodon, Hyasna, Ursus, Weasel, Hare, Rabbit, 

 Water Rat, Mouse, Dasyurus, Halmaturus, Kan- 

 garoo, and Kangaroo Rat. 



Birds : Pigeon, Raven, Lark, Duck, &c. 



Fishes : (in the formation generally) more than 100 

 species now extinct, which belong to more than 40 

 extinct and as many living genera. 



Insects: 162 genera of Diptera, Hemiptera, Coleop- 

 tera, Aptera, Hymenoptera, Neuroptera, Orthoptera. 



Shells : In the newer Pliocene period 90 to 95 per 

 cent, of living species ; 35 to 50 per cent, in the older 

 Pliocene; 17 per cent, in the Miocene; and 3*5 in 

 the Eocene, amounting in all to 4000 species. 



Plants: Poplars, Willows, Elms, Chestnuts, Syca- 

 mores, and nearly 200 other species, seven-eighths of 

 which are monocotyledonous or dicotyledonous. 



ALLUVIAL PERIOD. 



Man, and mcst of the other species of existing animals and plants. 



The manner in which organic remains have been preserved varies with the nature of the 

 deposit in which they are embedded. In the more recent rocks, the entire skeletons of 

 animals have been found, which have scarcely undergone any alteration, but more 

 frequently the harder parts alone occur, and with these the teeth are met with most 

 abundantly, still retaining their sharp edges and enamel. Shells also are common in 

 strata of very high antiquity, as perfect in form as if newly picked up on the shore of the 

 ocean ; and microscopic animals, which the slightest disturbance must have crushed, 

 appear uninjured, which proves that they must have lived and died on or near the spot 

 where they are found, have been deposited at the bottom of very quiet waters, and that 

 the consolidation of the strata was a very gradual and uninterrupted process. Dr. Mantell 

 remarks, that in his early researches he fell into the error of supposing that all fossils 

 must necessarily be petrifactions, and threw away many beautiful shells that were associated 

 with ammonites in the marl at Hornsey, supposing, from their perfect state, that they had 

 been accidentally imbedded, and were not genuine fossils. " But the state of preservation," 

 he adds, " and the degree of change which an organic body has undergone in the mineral 

 kingdom, have no necessary relation to its antiquity. The shells in some of the ancient 

 secondary strata are frequently as perfect as those of modern tertiary deposits. I have 

 collected, in the lowermost clays of the Wealden, fresh-water shells having traces of the 



