1 68 THE HABITAT OF THE ETJRYPTERIDA 



dence, be it palseontological, geographical or stratigraphical, to show 

 that these Devonic red beds were laid down in lakes. The attempt 

 to prove this theory has, as is so often the case in the development 

 of science, led to careful observations by many men, to the formula- 

 tion of alternative theories and to the collection of a great mass of 

 valuable data. That the first theory may perhaps prove incorrect 

 is of small importance compared to the fact that it made geologists 

 realize that there was a problem to be solved, and spurred them on 

 to its solution. This lacustrine theory, however, has had a longer 

 life than is usually allotted to first theories, for it has held on to the 

 present day and still has more adherents than has any later hypothesis. 

 The monograph by Sir Archibald Geikie "On the Old Red Sandstone 

 of Western Europe," published in 1878, embodied such an elaborate 

 discussion of the various lakes of the Devonic period and so many 

 field observations were adduced to back up the theoretical statements 

 that later writers have with few exceptions considered that the 

 lacustrine origin for the Old Red sandstone was proved beyond any 

 further question. To be sure, one or two heretical geologists have 

 raised objections to these ancient lakes and have preferred to think 

 that the Old Red was a marine deposit formed under particular and 

 inimical conditions. Within the last ten years both of these inter- 

 pretations have been questioned by not a few, and although the 

 majority of geologists unhesitatingly accept the older ideas, particu- 

 larly favoring the lacustrine theory, nevertheless, there is an ever- 

 increasing tendency at the present time to recognize the fact that all 

 continental formations need not necessarily be deposited in large 

 bodies of standing water. Thus the ultra-modern school of geologists 

 champions the importance of fluviatile deposits in the past, insisting 

 especially upon the fact that such deposits are spread out in large 

 part on the land and not in lakes or inland seas. This school of 

 "terrestrial" as opposed to "aqueous" geologists, found its earliest 

 leaders in Johannes Walther and Albrecht Penck, later disciples in 

 this country being Professors Grabau and Barrell. The last two as 

 well as Walther and Goodchild have argued the dominantly conti- 

 nental origin of the Old Red sandstone, Professor Grabau arguing 

 on the basis of the field evidence and on lithological and palaeonto- 

 logical grounds; and Professor Barrell from the standpoint of the 

 physical conditions which must have prevailed at that time. These 

 various theories will presently be taken up and the evidence for each 

 will be discussed. 



