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GEOLOGY: J. BARRELL 
DOMINANTLY FLUVIATILE ORIGIN UNDER SEASONAL 
RAINFALL OF THE OLD RED SANDSTONE 
By Joseph Barrell 
DEPARTMENT OF GEOLOGY, YALE UNIVERSITY 
Received by the Academy, July 17, 1916 
The Devonian system is represented in the British Isles by a series of 
rocks many thousands of feet in thickness, none of which, except in the 
south of England, hold marine fossils. Red sandstones constitute the 
predominant exposures, the colors ranging from light red to deep choco- 
late-brown, but in places are also found sandstones and shales of green, 
gray, or yellow colors. Besides the sandstone, the system includes 
much shale and conglomerate, the latter in places consisting of large- 
sized and subangular debris. Much volcanic material is intermixed in 
certain localities. This system of rocks, so distinct from the marine 
formations, has been familiarly known since the days of Hugh Miller 
as the Old Red Sandstone. 
The sediments are mostly barren of organic remains, but at certain 
horizons many fossils have been found, — plant fragments, estheria, 
scorpions, myriopods, eurypterids, ostracoderms, and fishes. Several 
distinct faunas are found, representing successive epochs. These fossil 
faunas contain the oldest known ganoid fishes and the oldest well pre- 
served representatives of those primitive and spinose sharks, — the 
acanthodeans. Ostracoderms are- well represented also. In contrast 
to this abundant preservation of chordates in certain horizons of the 
Old Red Sandstone, the rocks of earlier geologic periods show only rare 
and usually fragmentary remains belonging to this phylum. 
Our own ancestral line is regarded as having ascended through elas- 
mobranchs and crossopterygian ganoids. These groups evidently flour- 
ished at the time of the Devonian period within the environment under 
which the sediments of the Old Red Sandstone were laid down. If, 
then, we can determine the conditions of origin of those sediments we 
shall restore by so doing the life surroundings of the primitive ances- 
tral vertebrates; life surroundings which were related to their passage 
from the realm of the waters to that of the land and air. 
Godwin-Austen, noting the distinctness of the Old Red Sandstone 
formations from the typical marine Devonian, was led to a view in 1855, 
previously maintained by Dr. John Fleming, that the sediments were 
laid down in great freshwater lakes or inland seas. This interpretation 
rapidly supplanted the older view advocated by Hugh Miller, that the 
Old Red Sandstone was of marine origin. This lacustrine interpreta- 
