CLINTON GROUP. 
75 
eastern part of Williamson, a little north of the R idge road, the shale is completely charged 
with them, and very black and brittle, as if from carbonaceous matter derived from the fossil. 
The same character of the slate containing them, is noticed on the Genesee. This fact, and 
other similar ones, together with the carbonaceous nature of the fossil, would argue against 
placing these bodies among the calcareous polyparia. The specimen figured, resembles in 
some degree the G. Ludensis (Silurian System, PL 26, figs. 1 and 2); but in ours the serras 
are longer, less closely arranged, and the whole individual more delicate. Since also this 
fossil is found in rocks much lower than the Ludlow rocks of England, the probability of its 
being a distinct species is increased, and a specific name indicating its position is given. 
The shale associated with the iron ore at the Wolcott ore bed, though apparently holding the 
place of the upper green shale, contains an assemblage of fossils mostly different from those 
of that rock in other places, and also differing from those of the group generally in the Fourth 
District. Several other forms occur besides those presented in the following illustration, all 
differing as much from the ordinary ones ; while at the same time no fossil was found asso¬ 
ciated with them, which is common to the group elsewhere. This circumstance, however, 
adds but another fact to the many, regarding the geographical distribution of fossils in this 
group, and proving that upon the lithological character of the products depended, in a great 
degree, the organic forms which inhabited the bed of the ocean. 
An exhibition of the lithological development of the Clinton group at different points along 
its range, together with the fossils of each division, furnishes an instructive illustration of the 
nature and products of geological formations. We have here changes in the space of two 
hundred miles, as great as in other formations, when traced over an extent of as many thou¬ 
sands. The two extremities of the group within the State present scarcely any features in 
common, either fossil or lithological. 
While this group contains an assemblage of fossils peculiar to itself, and marking it as 
clearly as other formations are distinguished by similar characters, a few forms link it with 
the next group in the ascending order. The Strophoviena depressa appears here as its lowest 
position, and continues through several succeeding rocks. Th e Delthyris radiatus, and a 
smooth species of Atrypa, are also common to this group and the Niagara, not appearing in 
any higher position. The Catenipora escharoides, which is abundant in the upper part of 
the Niagara, first appears in this group. 
The forms presented in the illustration No. 18, are from the shale of the Wolcott ore bed. 
