New York State Museum 



LIMESTONES OF CENTRAL AND WESTERN NEW YORK 



INTEKBEDDED WITH 



BITUMINOUS SHALES OF THE MARCELLUS STAGE 

 WITH NOTES ON THE NATURE AND ORIGIN OF THEIR FAUNAS 



BY JOHN M. CLARKE 



Plate 8 



The peculiar aspect of the fauna accompanying the dark Mar- 

 cellus shales is familiar to every field worker in the geology of 

 New Y'ork. It is a small congeries of. diminutive and tenuous 

 shelled creatures, such as O r b i c u 1 o i d e a m i n u t a, C h o - 

 n e t e s m u c r o n a t u s , L i o "r h y n c h u s 1 i m i t a r e among 

 the brachiopods, A c t i n o p t e r i a m u r i c a t a , P t e r o - 

 c h a e n i a f r a g i 1 i s and a few other shells among the lamelli- 

 branchs, usually referred to L u n u 1 i c a r d i u m and P a n- 

 e n k a , the cephalopods Orthoceras subulatum, 

 Parodiceras, and the pteropod Styliolina fissur- 

 e 1 1 a in great abundance. In all bituminous beds of like char- 

 acter in the cider paleozoic there is a certain uniformity of 

 expression in the faunas, a sort of convergence, no doubt induced 

 in considerable measure by the circumstances under which 

 the eediments were deposited and the organisms have existed. 

 The latter, whatever their zoologic po'sition, show evidence 

 both in their small form and thin shell of having yielded in 

 some degree to the unfavorable influences of a shallow sea in 

 its influx on the epicontinental plateau.. It is quite evident that 

 the fauna, small as it is, is not homogeneous and can not represent 

 a single bathymetric facies. We shall observe from the consid- 

 erations following that, as a whole the fauna was introduced 

 within the confines of New York before the cessation of Onon- 

 daga limestone deposition; furthermore present evidence seems 

 to indicate that it was an invader from the southeast along the 

 inner or Appalachian, face of the interior sea. 



In the common and historic employment of the term Marcellus 

 shales as an expression of a lithologic unit, it has been usage to 

 include therein whatever slight variation in sedimentation these 



