RELATION OF BIOLOGY TO GEOLOGICAL INVESTIGATION. 283 



of paramount importance in connection with all practical investiga- 

 tions of that kind. 



The value of fossils in this respect is as purely practical as is that 

 of any other aid to geological investigation, and it may be made avail- 

 able without reference to their great value in other respects. 



Although all fossil remains are valuable for this practical use, those 

 of aquatic faunas are more valuable than any others. 



Remains of nonmarine faunas are of similar value for this purpose 

 to those of marine origin. 



