FOSSILS OF THE BLACK SLATE. 



65 



Tig. ». 



EUiptocephala asaphoides. 



No. 1, 13 a large individual, much flattened by pressure : the natural joints of the slate pass through the specimen. 

 The tail and a portion of the body are wanting. I have named this EUiptocephala asaphoides. The ellipse 

 upon the buckler appears to be a characteristic marking, while the ribs and middle lobe resemble very 

 strongly the same parts of the Jlsaphus tyrannus. In its perfect form, the ellipse seem3 to belong to the 

 old and perfect individual. 



No. 2, is the head of a small individual of the same species. The ellipse in this individual has an anterior segment 

 not to be seen in No. 1, which I suppose may be obliterated by age. 



No. 3, is a fragment of a trilobite probably, but the ribs bear a different character from those we generally meet with. 



§ 3. Taconic slate, with its subordinate beds. 



Characters of the Taconic slate. Reasons for the opinion that the coarser beds are not metamorphic. A'atural 

 joints. Enumeration of the principal beds ; their strike. Reasons for making the Hoosic roofing slates sui- 

 ordinate to the Taconic slate. Discovery of fossils : Fucoides and A'ereites. Supposed tube of a JVertites in 

 the coarse slates of Brunswick in Rensselaer county, JVew- York. 



It may be described as an even-bedded aluminous slate, varying from the finest possible 

 grit to one that is coarse and rather uneven-bedded, and passing into a rock having many 

 of the characters of a sandstone. The fineness appears not to depend upon its distance from 

 the western edge of the formation, or on its nearness to the present primary schists on the 

 east ; since the mass 7 (Fig. 7, page 19) is a coarse sandstone in the midst of fine argilla- 

 [Agricultural Report.] 9 



