TRENTON CONGLOMERATE OF RYSEDORPH HILL ( 



The intercalation of a similar bed in Normans kill graptolite 

 shale, at Schodaek Landing, 20 miles farther south, was made 

 known by S. W. Ford. 1 He describes, it as being 2 feet thick, and 

 in part, somewhat brecciated in appearance. From the mode of 

 occurrence of this bed, he has no doubt that it is a regular mem- 

 ber of the slate formation. It furnished to him : Isotelus 

 g i g a s , Calymmene s e n a r i a , D a 1 m a n e 1 1 a t e s t u - 

 d i n a r i a , P 1 a t y s t r o p h i a b i f o r a t a var. lynx, 

 Plectambonites sericea, Rafinesquina alter- 

 n a t a, and the hemispheric variety of Chaetetes 1 y c o • 

 per don. Both the limestone and its associated graptolitic 

 slates represent, in his estimation, the Hudson river group. A 

 visit to this interesting locality, which lies in the direct strike of 

 the Rysedorph hill and Moordener kill outcrops, convinced the 

 writer that it is a third exposure of the sarnie conglomerate bed, 

 containing the same groups of pebbles, though in different rela- 

 tive quantities. A fourth exposure of the same conglomerate, 

 observed by Ford just south of Schodaek Landing in a ravine, 

 running along the Columbia county line was not found again and 

 is probably covered at present by alluvial deposits. Still another 

 outcrop occurs near the boathouse of the Mohican canoe club, on 

 Papskanee island between Albany and Castleton. 



In all three localities the matrix consists of a dark gray to 

 black arenaceous limestone, which weathers into a drab sand- 

 stone, the Calciferous sandrock of Emmons. At the Moordener 

 kill it has a strong admixture of mud and also an admixture of 

 numerous fragments of shale, which, however, may have been 

 forced into it from the surrounding rock during the folding of 

 the beds. The pebbles, which by lithologic and faunistic differ- 

 ences can be divided into seven groups, are irregularly mixed, 

 mostly well worn, and of very different size ; the latter character- 

 istic in some measure depending on the hardness of the rock. 

 The seven groups of pebbles are : 



1 Lower Cambric limestone, represented by a single pebble 

 found in the Rysedorph hill conglomerate, which is in lithologic 



1 Am. jour. sci. 1884. 28:207. 



