348 - J. BARRELL FLUVIATILE ORIGIN OF OLD RED SANDSTONE 



interpret the meaning of the sediments which envelop the fossil — sedi- 

 ments which are the record of the environment of the living animal. 

 There is a side, then, to the ancient life history of the earth which belongs 

 to physical geology. It is as a physical geologist, and not as a paleontol- 

 ogist, that the writer has taken up the present problem, but with the 

 purpose of showing the relations between the environment and the evolu- 

 tion of air-breathing vertebrates. 



This article was prepared in essentially its present form in 190? and 

 made the basis of a paper on the causes of the evolution of land vertebrates 

 presented orally on December 26, 1907, to the American Society of 

 Vertebrate Paleontologists. 2 It was withheld from publication because 

 the writer hoped to make a personal field study of the Old Red Sandstone 

 formations of the British Isles- These plans did not materialize, but in 

 the meantime he has published a paper on the somewhat similar deposits 

 of the Appalachian geosyncline, 3 and he has also published a number of 

 critical studies on the interpretation of the sedimentary record. A broad 

 knowledge of the geologic problems involved and the correctness of the 

 criteria of interpretation are as important for drawing conclusions as are 

 the local facts to be interpreted ; this is the basis of judgment which has 

 led to a decision to publish the following study on the Old Eed Sandstone, 

 chiefly because of its bearings on the problems of the evolution of the 

 amphibians. 



The descriptions are taken from various memoirs, but experience shows 

 that the features which serve best as criteria of origin have been often 

 overlooked in the field or left undescribed in their reports by the older 

 geologists, partly because of a lack of appreciation of their significance, 

 partly because, even Avhen present, they are often as difficult to find'" as 

 fossils and require similar painstaking search of fresh exposures. 



The central conclusion reached in this paper is that the Old Eed Sand- 

 stone formations were not deposited in lakes or estuaries, nor are they of 

 desert origin. The analysis of their characteristics and comparison with 

 sediments now forming determines them to be river deposits accumulated 

 in intermontane basins. This is a kind of sedimentation not now found 

 in the British Isles. For a close analogy one may turn to the basin 

 deposits of the western United States laid down in the Tertiary period 

 between the growing ranges of the Cordillera. This reinterpretation of 

 the Old Red Sandstone of the British Isles is in line with that which has 

 gone forward in America during the past fifteen years in regard to the 



2 Abstract in Science, vol. xxvii, 1908, pp. 254, 255. 



3 The Upper Devonian delta of the Appalachian geosyncline. Amer. Jour. Sci., vol. 

 xxxvi, 1913, pp. 429-472 ; vol. xxxvii, 1914, pp. 87-109, 225-253. 



