THE SCOPE OF PALEONTOLOGY. n 



the earth during past periods of its history. Its object is to 

 eludicate, as far as may be, the structure, mode of existence, 

 and habits of all such ancient forms of life; to determine their 

 position in the scale of organized beings ; to lay down the geo- 

 graphical limits within which they flourished; and to fix the 

 period of their advent and disappearance. It is the ancient life- 

 history of the earth; and were its record complete, it would 

 furnish us with a detailed knowledge of the form and relations 

 of all the animals and plants which have at any period flourished 

 upon the land-surfaces of the globe or inhabited its waters ; it 

 would enable us to determine precisely their succession in time; 

 and it would place in our hands an unfailing key to the prob- 

 lems of evolution. Unfortunately, from causes which will be 

 subsequently discussed, the palaeontological record is extremely 

 imperfect, and our knowledge is interrupted by gaps, which not 

 only bear a large proportion to our solid information, but which 

 in many cases are of such a nature that we can never hope to 

 fill them up 



FOSSILS. The remains of animals or vegetables which we 

 now find entombed in the solid rock, and which constitute the 

 working material of the palaeontologist, are termed " fossils, " * 

 or " petrifactions. " In most cases, as can be readily understood, 

 fossils are the actual hard parts of animals and plants which 

 were in existence when the rock in which they are now found 

 was being deposited. Most fossils, therefore, are of the nature 

 of the shells of shell-fish, the skeletons of coral-zoophytes, the 

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

 plants. All such bodies are more or less of a hard consistence 

 to begin with, and are capable of resisting decay for a longer or 

 shorter time hence the frequency with which they occur in the 

 fossil condition. Strictly speaking, however, by the term " fossil " 

 must be understood " any body, or the traces of the existence of 

 any body, whether animal or vegetable, which has been buried 

 in the earth by natural causes" (Lyell). We shall find, in fact, 

 that many of the objects which we have to study as "fossils" 

 have never themselves actually formed parts of any animal or 

 vegetable, though they are due to the former existence of such 

 organisms, and indicate what was the nature of these. Thus 

 the footprints left by birds, or reptiles, or quadrupeds upon sand 

 or mud, are just as much proofs of the former existence of 

 these animals as would be bones, feathers, or scales, though in 



* Lat. fossus, dug up. 



