18 BIOLOGICAL SOCIETY OF WASHINGTON. 



Professor Marsh has published from that formation has heen 

 accepted as conclusive. Furthermore, the position of the for- 

 mation in relation to those which underlie and overlie it is 

 confirmatory of the received opinion as to its Jurassic age. 

 Notwithstanding this weight of evidence in the direction indi- 

 cated, the paleontologist of the Canadian Geological Survey has, 

 upon what I believe to be the mistaken identification of a com- 

 paratively small collection of imperfect and uncharacteristic fossil 

 shells, referred the formation bodily to the Middle Cretaceous. 

 When such a circumstance as this is possible it is certainly time 

 we should examine well the grounds of our conclusions before 

 we publish them to the world or base other results of our labors 

 upon them. 



While belief in the general applicability to all parts of the 

 world of the chronological scale now in common use will prob- 

 ably never be seriously shaken, it is plain that we must abandon 

 the idea that formations in widely separated parts of the world 

 were necessarily synchronous in their origin because certain por- 

 tions of their faunas or floras are similar. The custom has been 

 to recognize a complete chronological scheme of the formations, 

 of universal application, as already established, and to prosecute 

 the geology of every part of the earth with the express view of 

 making it conform to that scheme. But I submit that the 

 geology of each of the large divisions of the earth ought to be 

 studied independently, and untrammelled by preconceived notions 

 of necessary conformity to a foreign standard. In my opinion, the 

 time has not yet come for the construction of a complete and 

 detailed chronological scale for the whole earth, and that it will 

 not have fully arrived until the whole earth shall have been care- 

 fully studied. 



If geology were studied in the different divisions of the earth 

 with the ideas in view which I have indicated, its prosecution 

 would be relieved of much useless labor, as well as freed from a 



