BIGSBY PALAEOZOIC ROCKS OF NEW YORK. 379 



slate, full of iron-pyrites, with calcareous concretions here and there, 

 and courses of septaria, and has a strong general resemblance to 

 Utica Slate or Genesee Slate. This part ends upwards by a thin 

 band of limestone. 



The upper portion above this is a more fissile slate, of an olive- or 

 dark slate-colour. Both these divisions thin off westwards and south- 

 westwards. 



At the eastern commencement of this rock, its lithological cha- 

 racter is similar throughout the whole mass ; but, as we proceed west- 

 wards, we perceive a gradual separation of constituents, — the more 

 shaly portions, with some calcareous matter, taking the lower posi- 

 tion, while the sandy and slaty parts hold the higher place. This 

 occurs up to near the River Mississippi. 



The fine mud composing this rock, together with the nature and 

 delicate state of the fossils, show that this stratum was deposited at 

 a quiescent period. 



Transition. — The change from Corniferous limestone is everywhere 

 abrupt. A black argillaceous slate is laid down at once. The fos- 

 sils of the subjacent limestone are absent. 



Place. — It extends, east and west, through New York, with a 

 varying but narrow breadth, from near the River Hudson to Lake 

 Erie. A long strip of it proceeds from Lake Erie, S.S.W. into Ten- 

 nessee, in its proper stratigraphical position ; and it is seen alone (the 

 Hamilton group having thinned out) at Canary Fork and the Har- 

 peth Hills near Nashville in Kentucky, as well as near to and S.W. 

 of Louisville and at New Albany, Indiana. Small portions of coal 

 and much bitumen have been found at some of these places. This 

 shale is seen to rest on Corniferous limestone at Oneida Creek and at 

 Marcellus. 



Thickness. — This is 150 feet in Central New York, 30 feet in 

 Western New York, and still less on the north-west frontier of 

 Pennsylvania about Lake Erie. In Pennsylvania, more to the south, 

 the greatest thickness is 300 feet (H. D. Rogers). 



Fossils. — In the upper parts of this shale fossils are few ; and 

 these principally in the calcareous concretions. 



Our accounts of fossils in this and the other Devonian strata are 

 merely provisional, awaiting the appearance of James Hall's new 

 volumes. At present we have to state that Marcellus Shale pro- 

 duces twenty- two original species, chiefly Brachiopoda. It receives 

 but one fossil, a Brachiopod ; transmits five ; eighteen remaining 

 typical. It contains some remarkable organisms. The charac- 

 teristic genus Goniatites now appears for the first time. Desor (Bull. 

 S. G. France, 2 ser. ix. p. 314) says that in the black schists over 

 the cliff-limestone (equivalent to Marcellus and Genesee Slates) Mr. 

 Christie found many kinds of Goniatites, which Mr. Hall thinks 

 identical with those of the Carboniferous limestone of Europe. 



One has been named Goniatites Marcellensis ; but it is from the 

 lower part of the stratum in New York. 



The genus Lingula reappears here ; there are also a Productus, a 

 new Tentaculites, two Orthocerata, and the Dipleura Dekayi. 



VOL. XIV. PART I. 2 C 



