TRENTON CONGLOMERATE OF RYSEDOUl'H HILL 



101 



Trenton limestonej instead of ranging from the Trenton lime- 

 stone upward, so that the general aspect of the whole assemblage 

 of forms is decidedly- that of a fauna of the lower and middle part 

 of the Trenton period. 



Relative position of the black and gray Trenton limestones 

 In regard to the relative original position of the black com- 

 pact Trenton limestone and gray crystalline and reddish gray 

 compact Trenton limestone, which are mixed in the conglomerate, 

 it is to be remembered that the black limestone pebbles, in spite 

 of their strong admixture of strange types such as Ampyx and 

 Remopleurides, fail to show such a decided Lowville and Black 

 river limestone element as the gray limestone, and therefore 

 should be considered younger than the latter. This conclusion 

 is supported by the observation of several members of the black 

 limestone fauna in the matrix of the conglomerate at the Moor- 

 dener kill and at Schodack Landing, as shown in the following 

 tabulation. 



Fauna of matrix 



Streptelasma eoruicnlum. 



Pacbydictya sp 



Stroinatocerinm sp 



Raftoesquina alternata. .. 



Strophomeua incnrvata 



Plectamboiiites sericeus var 



asper 



P. pisum 



Orthis triceuaria 



Pterygometopus eallicephalus . 



Moordener 

 kill 



+ 

 + 

 + 



Schodack 

 landing i 



+ 



+ 



+ 



Occurrence of fossils in 

 pebbles 



black Treuton limestoiie 



black aud gray Treuton 

 limestone 



gray crystalline Trenton 



liniesrouo 

 black Trenton limestone 

 black Trenton limestone 

 gray aud black Trenton 



limestone 



This faunule would suggest that the conglomerate beds were 

 forme'd at a time when the organisms found in the black compact 

 limestone were still flourishing, and that both must be consid- 

 ered as falling within the same epoch, viz the lower Trenton. 



^ The matrix of the Rysedorph hill conglomerate, which is more sandy than that of the more 

 southern exposures, is filled only with comminuted fragnients of Rafinesquiua alternata, 

 Plectambonites sericeus, etc. 



