9 PAL^ONTOliOGY OF NEW-YORK. 



ding; and these being often close and well defined, while the lines of 

 bedding are obscure, give it the appearance of nearly vertical stratifica- 

 tion. This character prevails even when distant from any metamorphic 

 influences. These features distinguish the rock from any other in the 

 series; and even in its smaller outcrops, the vertical lamination has 

 been found a valuable guide in its identification. 



In the upper part we find a ^adual increase of calcareous matter, with 

 a diminution of the argillaceous material ; and it passes, by almost im- 

 perceptible gradations, to the Schoharie grit, which is marked by the 

 presence of numerous fossils. The upper beds of the Cauda-galli grit, and 

 also the lower beds of the Schoharie grit, preserve those peculiar mark- 

 ings which have been termed Fucoides cauda-galli. 



From the base of the Schoharie grit, we begin our investigation among 

 the fossils. In this rock we find, for the first time, a small number of 

 speciee which pass upward through the limestones of the Upper Helder- 

 berg group, and are more abundant in the Hamilton group('). At the 

 same time, also, we find a few species which are apparently identical 

 with some which we have known in the preceding rocks. These, however, 

 are so few, and being comparatively rare, the large number of new spe- 

 cies of the -same genera makes them inconsjiicuous, and we have essen^ 

 tially a new fauna. 



One of the most marked features of the change of fauna at this period 

 is the introduction, or appearance for the first time, of numerous species 

 of the Genera Cyrtocekas, Gyroceras, etc., with strongly lamellose or 

 fluted surfaces, and which are often ornamented by nodes er spines. 

 Some of the Orthoceratites are marked by sharp lamellose rings, and 

 some of the Gasteropoda are spinifcrous. The Trilobites of the Genera 



(1) Among those which begin their existence in this rock, occurring likewise in the Upper 

 Helderberg limestones and passing into the Hamilton group, Orthis vanuxemi?, Streptorhyri- 

 ckus chemungentis, Strophtnnetia demissa, S. perplana ^ S. crenistria, Spirifera fimbriata* , 

 Atrypa impressa = a variety of the A. reticularis ? while a larger number of species arft 

 conuDon to the grit and to the limestones above. 



* Two individuals of this species have been found in the Oriskany sandstone. 



