64 
BLACK SLATE. 
This slate is black, and each layer is often slightly glazed by a film of carbonaceous 
matter. Black calcareous layers appear in the slate only a short distance from the locality 
of the fossils, but diligent search there has not been rewarded by the acquisition of organic 
bodies of any kind. The laminae, which are quite thin, often exhibit intervening spaces 
of disintegrating red coarser and more friable particles than those composing the slate, in 
which we sometimes observe traces of organic matter, too obscure, however, to enable us 
to form an opinion of its nature. 
This mass has no essential character by which it can be distinguished from other slates, 
though the color may serve to remove it perhaps from the greenish taconic slate which 
appears but a short distance to the east. Assuming that its fossils are distinct from the 
rocks of this and the other systems, and provided they were as numerous as those of most 
fossiliferous rocks, there would be no difficulty in recognizing it. As the matter now stands, 
we have only three specimens of trilobites, and a fragment of something which appears 
to be an annelide, but may prove to be a trilobite that shall form a connecting link between 
the Crustaceans and Annelides. 
In consequence of the uncertainty in regard to the light in which this mass ought to be 
viewed, I dismiss the further consideration of it for the present. The character of the 
trilobites may be seen in the annexed figures. 
Fig. S. 
I 
Atops trilineatus. 
No. 1, is the head of a trilobite, which seems to belong to an intermediate genus between Calymene and Triarthrus. 
The head and part of the body are well preserved in one specimen; but the other (No. 2), is unfortunately 
badly worn. The latter I at first considered the same species as that represented by No. 1 ; but on further 
examination, I have little doubt that they are distinct. The ribs, of which I can easily count fifteen from 
the buckler to the posterior extremity of the specimen, are drawn too coarsely in the figure. The tail is 
acute, but not prolonged into a spine : there are no markings upon the buckler. The specimen, however, 
is too imperfect for a name, and would not have been noticed at all but from a wish to illustrate the rock as 
far as possible by its organic bodies. 
No. 1, I have named Atops trilineatus. The absence of eyes, however, is not a distinctive mark : the three species 
are blind. The Atops is evidently allied to the Triarthrus beckii , so abundant in the Utica slate ; the lines 
in this, however, are direct or transverse to the middle lobe : there is an additional pair in the Atops. 
