THEIR CHRONOLOGICAL STAGES. 271 



and subsisted chiefly by hunting and fishing. During the 

 deposition of the less ancient or middle formations the 

 earlier fauna had in a great measure disappeared, and species 

 of ox, deer, horse, wild-hog, wolf, bear, and other existing 

 genera had taken their places. To this period belong the 

 extinct species of ox, horse, and deer, which have been found 

 alike in Europe and America ; and perhaps also the gigantic 

 ostrich-like birds of Madagascar and New Zealand the 

 aepiornis, dinornis, palapteryx, and their congeners. The 

 men of Western Europe still fashion their stone and bone 

 tools and tree-canoes; but traces of underground stone- 

 dwellings, and pile-dwellings in lakes, with doubtful indica- 

 tions of metal implements, bespeak an advance and mark 

 the first stages from savagery to civilisation. During the 

 deposition of the more recent, the flora and fauna of every 

 region have remained much as we now behold them.* A few 

 general extinctions, like the dodo, solitaire, great auk, and 

 rhytina,t have been recorded ; hundreds of local extirpa- 

 tions and removals (like the original flora and fauna of our 



* According to Professor Heer, the native flora and fauna of Switzerland 

 have remained much the same since the time of the earliest lake-dwell- 

 ings, while the cultivated plants and domesticated animals have passed 

 into totally different varieties. If this observation be correct, it tends to 

 show that organic changes are slow or rapid in proportion to the physical 

 changes to which life is subjected, and that where the physical surround- 

 ings undergo slow and gradual mutations (which is the common course of 

 nature) plants and animals may exhibit little variation for ages. It is 

 thus that the specific changes recorded by Palaentology afford the strongest 

 evidence of the incalculable lapse and length of geological time. 



f The circumstances connected^with the extinction of the dodo, soli- 

 taire, and great auk, are well known. The rhytina, a phytophagous 

 Sireiiian, discovered by Steller on Behring Island in 1741, is also consid- 

 ered as completely extirpated the last individual having been killed in 

 1768. Unlike the manatees or sea-cows, the rhytina was edentate, having 

 special bony palatal apparatus for the crushing of its food. Its sub-fossil 

 remains (from 8 to 24 feet in length) are now eagerly sought after for our 

 public museums, and one or two specimens, we believe, were exhumed in 

 1864. 



