PALEONTOLOGY. 123 



especially such as are most nearly allied to those occur- 

 ring in the fossil state. When in the possession of such 

 knowledge, a study of the fossil contents of a bed, pre- 

 suming them to exist in sufficient abundance, tells him 

 at once whether the formation was marine, estuarine, 

 lacustrine, or terrestrial ; in the three former cases the 

 fossils will be for the most part remains of invertebrate 

 aquatic animals, and an examination of the number and 

 forms of these will greatly help him to form an opinion 

 as to whether the rate of deposition was slow or rapid, 

 whether the water was deep or shallow, near shore or 

 far from land. 



Finally, an acquaintance with the different faunas and 

 floras, which have at different times inhabited the world 

 and formed part of the general succession of life upon. 

 the earth, enables the palseontologist to estimate the 

 .relative age of any particular group of fossils, and to 

 assign them to their probable place in the geological 

 series. In the absence of organic remains, indeed, there 

 is often only slight evidence towards the solution of such 

 problems, and, except where the relative position and 

 lithological characters of the rocks are very marked, the 

 fossil evidence is of great use in confirming the conclusions 

 derived from an examination of the strata themselves. 



The important doctrine that strata may be identified 

 by their fossil contents was first taught by William 

 Smith, and is thus expressed in a sentence extracted 

 from his " Stratigraphical System :" " Organised fossils 

 are to the naturalist as coins to the antiquary ; they are 

 the antiquities of the earth, and very distinctly shew 

 its gradual regular formation with the various changes 

 of inhabitants in the watery element." 



