CONCLUSIONS TO BE DKAWN FEOM FOSSILS. 



conclusions can be accurately reached by an examination of 

 these. As regards the determination of the conditions of 

 deposition from the remains of aerial and terrestrial animals, 

 or from plants, there is not such an absolute certainty. The 

 remains of land-animals would, of course, occur in " sub- 

 aerial " deposits that is, in beds, like blown sand, accumu- 

 lated upon the land. Most of the remains of land-animals, 

 however, are found in deposits which have been laid down in 

 water, and they owe their present position to having been 

 drowned in rivers or lakes, or carried out to sea by streams. 

 Birds, Flying Eeptiles, and Flying Mammals might also 

 similarly find their way into aqueous deposits ; but it is 

 to be remembered that many birds and mammals habitually 

 spend a great part of their time in the water, and that these 

 might therefore be naturally expected to present themselves 

 as fossils in Sedimentary rocks. 

 Plants, again, even when un- 

 doubtedly such as must have 

 grown on land, do not prove 

 that the bed in which they 

 occur was formed on land. 

 Many of the remains of plants 

 known to us are extraneous 

 to the bed in which they are 

 now found, having reached 

 their present site by falling 

 into lakes or rivers, or being- 

 carried out to sea by floods 

 or gales of wind. There 

 are, however, many cases in 

 which plants have undoubt- 

 edly grown on the very spot 

 where we now find them. 



Thus it is nOW eener 



mitted that the great coal- 

 fields of the Carboniferous age are the result of the growth 

 in situ of the plants which compose coal, and that these 

 grew on vast marshy or partially submerged tracts of level 



Fig. 12. Erect Tree containing Reptilian 

 a(J_ remains. Coal-measures, Nova Scotia. (After 

 Dawson.) 



