" FOSSILISATION. 3 



animals or plants which are now extinct that is to say, 

 which no longer are in existence, but have entirely disap- 

 peared from the earth's surface. In some cases, however, 

 fossils are the remains of recent animals that is, of animals 

 which are still found in a living condition upon the globe. 

 The term " sub-fossil," sometimes applied to these, has been 

 more appropriately applied in another sense, and is best dis- 

 carded in this connection. In any case, the fact that a given 

 specimen belongs to an extinct species of animal or plant, or 

 that it is referable to some existing form, does not enter in 

 any way whatever into the determination of the question as 

 to whether or not it is truly a fossil. If such a specimen is 

 found in those portions of the earth's crust which we can 

 show by other evidence to have been formed prior to the 

 establishment of the existing terrestrial order, then it is a 

 fossil ; while any remains, even though belonging to the 

 same animal, which are found in deposits which have been 

 formed during the historical period, would properly fall to be 

 studied by the zoologist or the botanist, and would not rightly 

 be termed " fossils." It must be admitted, however, that in 

 approaching the " Eecent " period of the earth's history, it 

 becomes a matter, of difficulty indeed, a matter of impos- 

 sibility to draw any precise line between fossil and recent 

 specimens. 



The terms " fauna " and " flora " are employed in Palre- 

 ontology much as they are by the naturalist, to mean the 

 entire assemblage of the animals or of the plants respectively 

 belonging to a particular region or a particular time. Thus 

 we may speak of the " fauna " of the Carboniferous Period, 

 or the " flora " of the Tertiary Epoch, or the fauna of the 

 Chalk, or of any other set of beds. 



FOSSILISATION. 



The term " fossilisation " may be applied in a general sense 

 to all the processes through which an organic body passes in 

 order to become a fossil. Here we need only consider the three 

 leading forms in which fossils present themselves. In the 

 first instance, the fossil is to all intents and purposes an actual 



