DEFINITION OF FOSSIL. 25 



purely scientific in their nature ; but they form the basis for an 

 intelligent comprehension of the third department of the sci- 

 ence. The last is popularly regarded as the only one of the 

 three sections worthy of notice, since it is directly more useful 

 than the others. This notion, however, is very misleading, for 

 without a full consideration in the first place, from a purely sci- 

 entific side, the usefulness of these guides to mineral wealth 

 ceases to exist. 



From the biological standpoint, the remains of ancient life 

 are of first importance in their bearing toward the phyloge- 

 netic history of existing organisms. With the large majority of 

 the living animals and plants, the relationships with one another 

 can be made out only through forms now long extinct. Many 

 large and interesting groups are not represented at all at the 

 present day among the faunas and floras of the globe. A 

 knowledge of their former existence is, therefore, of invalua- 

 ble aid in the attempt to make more complete the conception 

 of the great plan of life. There are, besides, isolated living 

 forms whose genetic relations long remained enigmatical, until 

 it was discovered that they were very abundant in ages gone 

 by; for they proved to be the lingering remnants of once 

 flourishing and long-lived tribes now on the verge of extinc- 

 tion. 



The second great function of fossils in biology pertains to 

 the geographical distribution of organisms in former periods 

 of the earth's history, and to the range of forms in time. The 

 former consideration refers directly to the present limits of 

 animals and plants in space ; the latter to the deciphering of 

 the antiquity of the living zoological groups. 



Broadly understood, the term "fossil" is applicable to any 

 organic traces of life naturally entombed in the earth's crust. 

 But the various ways in which the hard parts of organisms are 

 preserved give them widely different values as stratigraphical 

 criteria. Accordingly the most important phases are : First, 

 when the hard parts have suffered only slight changes in chemi- 

 cal composition, with the loss of merely the animal matter and 



G— 3 



