INTRODUCTION. * 



a prosecution of the study of Palaeontology, and such de- 

 tails of these sciences as may be deemed requisite will be 

 introduced in the proper place. The materials, again, which 

 fall to be studied by the palaeontologist, are drawn entirely 

 from the proper province of the geologist. Fossils are de- 

 rived from rocJcs. It will therefore be necessary to trespass 

 to some extent upon the peculiar domain of the geologist, 

 and to obtain some knowledge of the origin, composition, and 

 mode of occurrence of the rocks from which Palaeontology 

 obtains its materials. Lastly, Palaeontology, apart from its 

 own importance as an independent science, is employed by 

 the geologist to assist him in his determination of the chron- 

 ological succession of the materials which compose the crust 

 of the earth. Palaeontology, therefore, in one of its aspects, 

 is a branch of geological science, and requires separate study 

 in its relation to historical Geology. 



DEFINITION OF FOSSILS. 



All the natural objects which come to be studied by the 

 palaeontologist are termed " fossils " (Lat. fossus, dug up). 

 In most cases, fossils, or, as they are often termed, " petri- 

 factions," are actual portions of animal or vegetable organ- 

 isms, such as the shells of Molluscs, the skeletons of Corals, 

 the bones of Vertebrate animals, the wood, bark, or leaves of 

 plants, &c. ; and these may be preserved very much in their 

 original condition, or may have been very much altered by 

 changes subsequent to their burial. Strictly speaking, how- 

 ever, by the term " fossil " is understood " any body, or the 

 traces of the existence of any body, whether animal or vege- 

 table, which has been buried in the earth by natural causes " 

 (Lyell). We shall find, therefore, that we must include 

 under the head of fossils objects which at no time themselves 

 formed parts of any animal or vegetable, but which, never- 

 theless, point to the former existence of such organisms, and 

 enable us to reason as to their nature. Under this head 

 come such fossils as the moulds or " casts " of shells and the 

 footprints left by various animals upon sand or mud. 



In the great majority of cases fossils are the remains of 



