BIGSBY — PALEOZOIC ROCKS OF NEW YORK. 



363 



Place. — It is only known in the east of the State, and has been 

 most carefully examined by Messrs. Gebhard, of Schoharie. It 

 extends along the base of the Helderberg Mountains, and along the 

 River Hudson. It can also be traced west as far as Herkimer 

 County. 



Its place in the upper stage of the Silurian system is well made 

 out. At Schoharie it rests upon the green shale of the Clinton, and 

 continues westward above that group always, and beneath the Onon- 

 daga-Salt group (Hall, Pal. ii. 321). 



Position. — This is the same as that of the Niagara group. 



Thickness. — About four feet. 



Fossils. — It is chiefly occupied by broken zoophytes, mostly Favo- 

 sites. Of these but few species have been named — perhaps from 

 their being so comminuted. We find Columnaria incequalis ; Chce- 

 tetes niagarensis ; Diplophyllum coralliferum ; Stromatopora con- 

 centrica and S. constellata ; Catenipora escharoides. The New 

 York geologists do not mention here a single Bryozoan, Echino- 

 derm, Cystidean, or Orthoceratite. There are only two Leptcence, 

 two Orthides, three Spiriferi, five Atrypce, and one Strophodonta 

 (textilis}. 



In the order Monomyaria are met with here four Aviculce and one 

 Tellinomya, no Dimyaria, seven Gasteropoda. These fossils show 

 that the thin edge of the Niagara, as we may call the Coralline 

 Limestone placed in the east of the State, sympathizes in the fossil- 

 relations of the arenaceous deposits around. The conditions, we may 

 remark, under which the sediment of the east and west parts of the 

 State was deposited were very different, and the depth of the Silu- 

 rian sea may have been unequal at that time ; therefore we have a 

 varied fauna and the Coralline Limestone of Schoharie. 



Fossils typical. — Even in so limited a thickness, this limestone 

 presents us with thirty typical forms, as now known. They are — 



Columnaria inaequalis. 

 Diplophyllum coralliferum. 

 Stromatopora constellata. 

 Leptaena bipartita. 



(Stroph.), n. sp. 



Orthis interstriata. 



orbicularis. 



Spiriferi, two new species (Hall). 

 Atrypa limseformis. 



lamellata. 



nucleolata. 



, n. sp. 



Strophodonta textilis. 

 Tellinomya aequilateralis. 

 Murchisonia obtusa. 



Murchisonia terebralis. 

 Avicula limaeformis. 



securiformis. 



subrecta. 



n. sp. 



Pleurotomaria subdepressa. 

 Bellerophon aurieulatus. 

 Bucania, sp. indet. 



, n. sp. 



Oncoceras expansum. 

 Trochoceras Gebhardi. 



turbinata. 



Phragmoceras, sp., indet. (near the 



junction with the Onondaga- 



Salt group) (29). 



Leperditia alta is probably here, and typical (Hall and Mather). 



Fossils occurrent in Europe. — Not one in this rock, except as 

 considered a part of the Niagara group. 



VOL. XIV. PART I. 2 B 



