242 
GEOLOGY OF THE FOURTH DISTRICT 
This fossil occurs in short rigid fragments, lying in great confusion, spread over the sur¬ 
face of the thin flagstones of the middle part of the group. It is only by its general form and 
the arrangement of the fragments that it can be characterized. It can be found in all localities 
of the flagstones, and, from the extensive use of these, it may be seen on the sidewalks of all the 
villages upon or near the group. Some of the finest specimes I have ever seen are used in 
the streets of Geneva, and the numerous little ridges upon their surfaces will be recollected by 
every one who has been in this village. At Penn-Yan the same character is presented in the 
flagstones, but less perfect than at Geneva. 
Almost all the thin sandstone layers present this appearance, and the beds of the ravines 
are strewed with them. 
This species of fucoids disappears towards the upper part of the group, where the sand¬ 
stone becomes thicker and in greater proportion, and gives place to another species. This 
consists of small round stems, extending vertically through the strata, as if they were growing 
at the time the sand was deposited around them. 
105 . 
This species has always been found characteristic of the upper part of the group; and 
although in the higher rocks there are sometimes vertical fucoids, they never present the same 
character as those of Portage. 
It may be seen at the Lower falls of Portage, and in many of the sandstone strata above 
this ; but it is most abundant in the upper sandstone at Portage, and the terminating mass of 
the group is everywhere known by its presence. 
