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 trilobiles, 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. 



B"ig. S. 



Atops tfilineatas. 



No. 1, is the head of a trilobite, which seems to belong to an intermediate genus between Calymcne and Triartkrus. 

 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 Jltops is evidently allied to the Triarthriis bcckii, so abundant in the T'tica slate ; the lines 

 in this, however, are direct or transverse to the middle lobe : tliere is an additional pair in the Atops. 



