8 TRIASSIC FISHES AND PLANTS. 
iron to protoxide, and makes the color, so far as influenced by the salts 
of iron, gray, green, or blue. Where the organic matter is in very large 
quantity it imparts the characteristic color of carbon, and makes the shale 
or limestone which contains it black. 
The general absence of organic matter in the Triassic rocks is doubt- 
less due to the circumstances under which they were deposited; that is, in 
brackish water, which is always unfriendly to life, and perhaps was sub- 
ject to high tides, which caused physical commotion, another unfavorable 
condition. We can imagine the circumstances attending the accumulation 
of the Triassic sediments to have been somewhat like those which now 
prevail in the Bay of Fundy, where the advance and retreat of a bore, or 
very high tide, keeps the water always in violent motion and turbid, and the 
alternating extremes of ebb and flow forbid the occupation of the littoral 
zone by either animals or plants. The gray and blue shales of Boonton 
and Sunderland contain an abundance of organic matter, of which sufficient 
would be furnished by the fishes to partially deoxidize the iron deposited 
with them, while the black shales of Plainfield and Weehawken, N.J., and 
Durham, Conn., are colored simply by the abundance of carbonaceous matter. 
An illustration of the truth of the views here proposed is found in the dif- 
ference between the colors prevailing in the Palisade area and the Richmond 
basin. In the former the rocks are, as has been stated, generally very 
barren of fossils and the color is mostly reddish, while in the latter the 
quantity of organic matter is large and the color of the rock is blue, gray, 
or black. 
GEOLOGICAL EQUIVALENTS OF OUR TRIASSIC ROCKS. 
The age of the series of rocks which have been called Triassic on the 
preceding pages has been much discussed. Maclure considered them the 
equivalent of the Old Red Sandstone of Scotland, being influenced by 
the similarity of their lithological characters. 
Mr. Richard C. Taylor, for a time at least. entertained the opinion that 
the group of rocks we are now considering belonged to the Coal Measures, 
being led to this conclusion by the presence of coal beds in the Richmond 
basin and the general resemblance to the Coal Measures of Pennsylvania 
exhibited by the associated rocks. A single one of the abundant fossil 
