10/4 PRINCIPLES OF STRATIGRAPHY 



preserved in the strata of the earth, and these we call fossils, or 

 petrefactions." (Steinmann, Einfiihrung in die Palaontologie, 

 translated.) This definition in terms of past geologic time is an 

 arbitrary one, and is not based on any distinction in character 

 between the remains which were bnried before and those which 

 were buried during the present geologic epoch. Thus the marine 

 shells in the post-glacial elevated clays of northern New England 

 and Canada ( Leda, Saxicava, etc.) diiTer in no wise from those 

 of the same species buried in the modern deposits off the present 

 coast. 'Tn the former case the strata have been elevated several 

 hundred feet ; while in the latter case they still retain their original 

 position, or, at least, have experienced no appreciable disturbance. 

 In like manner many of the Miocenic and Pliocenic shells are not 

 only of the same species as those recently buried on neighboring 

 shores, but the changes which they have undergone since burial are 

 frequently not greater than those experienced by shells buried in 

 modern accumulations. The difference in the alteration is merely 

 one of degree, and with proper discrimination specimens can be 

 selected which show all grades of change, from the unaltered state 

 of shells in modern mud-flats to the crystalline condition of an 

 ancient limestone fossil, in which the original structure has been 

 completely lost." (Grabau-13 :p7, pS.) It is thus seen that it is 

 far more logical to extend the term "fossil" so as to include all 

 remains of animals and plants preserved from the time of the 

 earliest fossiliferous strata to the present. This is the position 

 taken by Lyell, who defines a fossil as : "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." In this definition 

 made by the geologist the time element is entirely omitted and in 

 this respect it contrasts markedly with the definitions quoted above 

 from pal?eontologists. Of the latter, however. D'Orbigny forms 

 an exception, for he considers the term "fossil" to comprise "all 

 bodies or vestiges of bodies of organisms buried naturally in the 

 rocks of the earth and found to-day, except when actually in the 

 living state." (Cours filementaire de Paleontologie, Vol. I, p. 13.) 

 Geikie, too, neglects the time element in his definition of a fossil. 

 He says : "The idea of antiquity or relative date is not necessarily 

 involved in this conception of the term. Thus, the bones of a sheep 

 buried under gravel and silt by a modern flood and the obscure 

 crystalline traces of a coral in ancient masses of limestone are 

 equally fossils." (Text-book of Geology, 3d ed., p. 645.) This 

 general definition of a fossil is the one insisted upon by Grabau 

 and Shimer in "North American Index Fossils" (Volume I, page i.) 



