202 THE HABITAT OF THE EURYPTERIEA 



ancestors were marine. The Bertie fauna of North. America covers 

 an area of not over iooo square miles. The corresponding European 

 chronofauna is found in the Baltic Isles and Russian Provinces in 

 sediments similar in lithologic character to those in North America, 

 but the areal extent is small and circumscribed. In the Upper Siluric 

 of Bohemia and of Scotland the eurypterids occur within a very limited 

 area. But in the adjoining undoubted marine formations which lie 

 in the path of migration by marine waters, the eurypterids are want- 

 ing. The graptolite fauna of the Ordovicic is known throughout the 

 world, but the eurypterids are found only in the small area around 

 Catskill, New York. Similarly, eurypterids are found in the Wenlock 

 shales and limestones of Scotland, but not to the south in England, 

 nor in other Niagaran formations at the same horizon throughout the 

 world. 



The tremendous importance of the geological and geographical 

 distribution of the eurypterids has heretofore been overlooked except 

 by Professor Grabau, who has dwelt upon it in the discussion of the 

 most important occurrences, especially in North America. When the 

 factors of distribution are considered throughout the Palaeozoic and 

 on every continent, it will be seen that they constitute the gravest 

 objection of all to any marine, lagoon, or estuarine theory of habitat 

 that has been advanced. Again we must turn to a contemplation 

 of the present, for we must believe that the laws which control the 

 universe have always been undeviatingly constant and will always 

 remain so. Our great difficulty in reading Earth history correctly 

 lies in our failure to learn the laws; so much of the past appears to 

 our view not in the form of causes but of results. In the study of the 

 phenomena of the present, we are usually privileged to see both the 

 causes and the effects, and thus the opportunity is offered to ascer- 

 tain the laws, although in many cases our lack of knowledge or our 

 unreadiness, prevents us from taking advantage of this opportunity. 

 Thus we fail to learn and to formulate the laws which are operative 

 in every physical fact and phenomenon, visible or invisible. That 

 man we call a master who has discerned the laws ; he alone can inter- 

 pret with truth the marvels of this world and of other worlds; he 

 alone can prophecy, with a reasonable degree of certainty, the things 

 which are to come; and he alone, if he be a geologist, can reconstruct 

 along the lines of truth the former history of our earth. Therefore, 

 it behooves us to become acquainted with the laws which may be 

 studied today, before we attempt to formulate theories about the 



