ancestors were marine. The Bertie fauna of North America covers an area of not over 1000 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 he in the path of migration by marine waters, the eurypterids are wanting. 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 ascertain 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 interpret 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
