TRENTON CONGLOMERATE OF RYSEDORPH HILL 9 



5 This group consists of mostly small pebbles of a very hard, 

 compact limestone, intensely black when, fresh, but very soft 

 and of brownish tint when weathered. These were found in the 

 conglomerate of Rysedorph hill and the Moordener kill, none 

 being obtained at Schodack Landing. They contain a most inter- 

 esting fauna, new and peculiar species of trilobites, brachiopods, 

 and gastropods, described in another part of this paper. This 

 limestone will be cited in the descriptions and lists as " compact 

 black limestone." 



6 Very commonly on Rysedorph hill and rarely also at the 

 Moordener kill occur pebbles of a very hard, compact, fine 

 grained, dark gray limestone, which weathers into a reddish 

 gray rock, and therefore will be cited in this paper; as the 

 " compact, reddish gray limestone." It has been found to con- 

 tain rarely a few of the fossils of the preceding limestone, while 

 it never fails to contain ostracodes, some of the pebbles showing 

 the tiny, black, glossy fossils with wonderful distinctness. 

 The most common of these are B y t h o c y p r i s c y 1 i n - 

 d r i c a Hall, a variety of S o h m i d t e 1 1 a c r a s s i m a r - 

 g i n a t a Ulrich, and E u r y c h i 1 i n a reticulata Ulrich. 



7 The last group of pebbles consists of a light gray crystalline 

 limestone, which often changes into a veritable shell rock. The 

 greater number of these is largely made up of Plectam- 

 b o n i t e s s e r i c e a showing a varietal development, others 

 consist of R a f i n e s q u i n a a 1 1 e r n a t a or parts of I s o - 

 t e 1 u s g i g a s . This group of pebbles is by far the pre- 

 vailing class in the Rysedorph hill conglomerate, and is still com- 

 mon at the Moordener kill, but has become greatly diminished at 

 Schodack Landing, the relative quantity of these and the sand- 

 stone pebbles being, roughly stated, inversely proportional. 



A farther discussion of the character and composition of this 

 conglomerate bed can not be carried on advantageously till 

 after the description of the species and the determination of the 

 taxonomiic relations of the faunas of the last three groups of 

 pebbles. 



The unmistakable presence of pebbles of Ohazy limestone 



