226 
GEOLOGY OF THE FOURTH DISTRICT 
On the Genesee river, which affords the best development in the district, this group admits 
of the several subdivisions shown in woodcut 97 at the foot of the page.* 
98. 
View on Cashaqua creek. From a sketch by Mrs. Hall. 
l. Cashaqua Shale. 
This rock, in lithological and fossil characters, differs sufficiently from those above to be 
considered under a separate name. From its perfect development upon the Cashaqua creek, 
that name was applied to it before the examinations of the higher rocks had been completed. 
*97. 
The lowest rock here represented rests on the Genesee slate, and about eight feet from its base is marked with a band of 
black shale, similar to the Genesee in every respect. The three divisions of this group, as given in the woodcut, are plainly 
recognizable on the Genesee river, and to a great extent over the whole district. As we go east from this point, however, 
there is a constant increase of arenaceous matter, and in a westerly direction an increase of mud or shale. The whole can 
be better described under the three divisions above noticed. 
