PALJIONTOLOGY OF NE¥-YOEK. 



The descriptions and illustrations of the fossils in the third volume of 

 this work include those from the Lower Helderberg group and the Ori- 

 skany sandstone ; while the first part of the present volume, following 

 the formations in the ascending order, will embrace the Bbachiopoda of 

 the following rocks and groups : 



CHEMUNG GROUP ; 



PORTAGE GROUP, The Genesee slate, forming beds of passage ; 



TtJLLY LIMESTONE and 



HAMILTON GROUP, including the 



UPPER 

 HELDERBERG GROUP, including the 



Marcellus shale ; 



cohniferocs limestone, 



Onondaga limestone, 



Schoharie orit, and 



Cauda-galli grit, which rests upon the 



Oriskant sandstone. 



The CAUDA-GALLt GRIT is almost a non-fossiliferous rock ; a few frag- 

 ments of plant-like fossils, and the peculiar surface markings of the slaty 

 laminae, from which the name is derived, being the only objects resem- 

 bling organic bodies which have fallen under my observation. A single 

 specimen of Platyceras, similar to P. tortuosum of the Oriskany sand- 

 stone, has been found in this rock. 



The passage from the Oriskany sandstone to this "Grit," or (as it 

 usually occurs in many localities) arenaceous shale, or shale, is very 

 abrupt and strongly defined. The rock itself is usually a dark or nearly 

 black slaty grit, weathering to a grayish or brownish gray color, with 

 strong lines of jointing or lamination nearly at right angles to the bed- 

 [ Pal^ontoloot IV.] 1 



