34 Proceedings of tJie Ohio State Academy of Science 



and Pyrenees, over the river plains of northern India and eastern 

 China, such deposits are forming today or have been formed in 

 the past on a scale comparable with that of the Tertiary areas of 

 supposed lake deposits in the west. It would seem to have been 

 the unthinking acceptance of a traditional interpretation, which 

 assumed that such sedimentary deposits must have been made in 

 standing water. But little thought is needed to see that sands, 

 muds, and gravels are deposited subaeriallv bv streams, as well as 

 in lakes or seas. 



Davis called attention (iqoo) to the situation, in his paper 

 on The Fresh Water Tertiary Formations of the Rocky Moun- 

 tain Region. He here showed that Penck (1894) had already 

 recognized the possibility of the occurrence of fluviatile ( con- 

 tinental) deposits in the older rocks, and that Gilbert had already 

 applied this interpretation to some of the "lake" deposits of the 

 western plains area. Davis raised the whole question, suggested 

 criteria for discrimination between fluviatile and lacustrine de- 

 posits, challenged in particular two of the western Tertiary 

 formations, and put the whole matter on the modern basis. Since 

 then it has been necessary to treat each formation as a separate 

 problem, and the conception of the Tertiary as a "lake" age has 

 rapidly waned. Rather it was a time of extensive plains building 

 along mountain bases and over intermont basins by overloaded 

 depositing and wandering streams on leaving the mountains. 



Another result of this discussion has been to raise a doubt as 

 to the origin of many of the non-fossiliferous or sparingly fos- 

 silif erous deposits in other parts of the country ; deposits of the 

 older periods which formerly were unquestionably accepted as 

 marine ; and some of these formations are now coming to be 

 recognized as in part or in whole of subaerial origin, the deposits 

 of rivers. In the second case as in the first, we are driven to a 

 revision of our conception of past geography, for we can no 

 longer consider sandstones and shales, ipso facto, as indicating 

 the former presence of water areas. 



PALEOGEOGRAPHY. 



Another recent development we owe largely to the paleon- 

 tologists. In the last twenty-rive years an immense amount of de- 



