an exposure just before crossing the Rome, Watertown 
and Ogdensburg tracks, and another just beyond the rail- 
road. 
At Three River Point there is a quantity of shale that 
was thrown out by the workmen in digging for the foun- 
dation of the bridge. The shale is considerably darker 
than the green shale, and is more properly called a blue 
shale. It is the only exposure of its kind that I have as 
yet found in the county. 
As a rule, the shales composing this group are thin and , 
readily broken, and are usually largely colored with iron. 
Indeed, in many places, the iron ore beds found in this 
group form one of its chief characteristics. Although the 
group is usually quite fossiliferous, nevertheless, on ac- 
count of the poor exposures found here, and the small part 
of the group which they cover, we cannot obtain a repre- 
sentative collection of Clinton fossils from ovr county. A 
few small brachiopods, mostly Spirzfers, the Strophomena 
rhombowdalts, Strophodonta (sp.), together with numerous 
specimens of Fucoides, are all that J have as yet been able 
to find. 
Since several of the adjoining counties have this shale 
so much more advantageously exposed, we will find it 
more satisfactory to study this group at those places, or in 
the excellent gorges at Rochester, Lockport or Niagara, 
than to spend much time at the exposures found in our 
county. 
The Niagara Group is the next division of this period, 
which we will meet by continuing in our course toward 
the south. It is composed of two divisions, which are 
known as the Niagara Shale and the Niagara Limestone. 
It is these two layers that occur at the famous falls. At 
that place there is some eighty feet of limestone overlying 
an equal amount of shale. The same formation extends 
in an easterly direction across our entire State, gradually 
II 
