2 
at a particular place. The character of the sediments is only 
one of them. Other controls of equal and even greater import- 
ance are character of the bottom, depth of water, food, presence 
of other organisms, and character of the waters. If the sedi- 
ments of the same stratigraphic horizon be different, different 
fossil organisms may be expected ; if alike, they may contain the 
same organisms ; but other important factors in the environment 
may have determined the presence of a different group of 
organisms. As illustrative of this fact the following is to the 
point. In a north bay on Harbour island of the Mingan group, 
the common sea urchin, Strongylocentrotus drabachiensis, was 
seen in 1909 by the writer in thousands of individuals, the bot- 
tom being so thickly covered that there was no room for any 
other organisms of equal size. They were not seen in such 
abundance elsewhere and in some of the bays of the islands they 
were not seen at all. In some parts of the shallow water about 
Anticosti island this animal occurs in thousands and probably 
millions of individuals, but in other places with a bottom not 
superficially different not a single one could be observed. At 
Bird bay and Gull cliff near the east end of Anticosti island are 
thousands of sea pigeons, cormorants, guffs, and other birds. 
There are big cliffs at scores of other places on the island com- 
posed of exactly the same kind of rock and just as long, high, 
and inaccessible ; but birds are not present in such great numbers 
at any other place. What is the determining factor or factors 
in this variation? There must be some reason, but there is not 
one apparent. These thousands of birds mean that their bones 
and excretions and the skeletons of the food they eat are at 
present being deposited in considerable quantity about their 
habitat and that elsewhere about the island such material is 
not so abundant. In a recent paper Dr. T. Wayland Vaughn 
has given some information relating to faunal variation which 
should impress all geologists and particularly those engaged in 
stratigraphic work. 1 His illustrations are drawn from the 
distribution of the corals about the Cocos-Keeling islands. In 
the lagoon of this group are twenty-three species of corals; on 
the exposed barrier sixteen species. Only three species are 
Waughn, T. Wayland, Bull. 103, U.S. Nat. Mus., 1919, pp. 190-193. 
