100 NEW YORK STATE MUSEUM 



been found only in one specimen in the Trenton of Saratoga 

 county, and, for this reason, has little taxonomic weight, while 

 D a 1 ui a n i t e s achates, Leptaena r h o m b o i d a 1 i « 

 and B y t h o c y p r i s c y 1 i n d r i c a , having a wider distri- 

 bution, must be considered as strongly supporting the view otf 

 the Trenton age of this fauna, suggested by the fossils just named. 



In weighing the evidence furnished by the two groups of fos- 

 sils, those which have their typical development in the lower 

 epochs of the Trenton period, and those which are restricted to 

 the Trenton limestone itself, it is to be considered that the Low- 

 ville and Black river limestone element is largely represented by 

 ostracodes which, having been carefully studied in the west and 

 found to be quite markedly restricted to certain horizons, must 

 be regarded as fairly reliable horizon-markers. The forms from 

 the conglomerate bed of Bysedorph hill, however, show, with the 

 exception of E u r y c h i 1 i n a reticulata, certain differ- 

 ences from the western types which, it is true, may be more the 

 expression of difference of province than of epoch, but, in the 

 face of the strong Trenton limestone element with which they 

 are associated, can not be considered as furnishing conclusive 

 evidence. 



We have therefore somewhat conflicting evidence as to 

 the age of these beds, which in the writer's opinion is due 

 partly to the fact that the ostracode forms of the Trenton lime- 

 stone of New York have not vet been thoroughly collected and 



« c ft. 



studied, and partly due to the smallness of the fauna known aa 

 yet from the Lowville and Black river limestones of this state, 

 specially from the former. All that can be said, therefore, at 

 present in regard to the taxonomic relations of the fauna of the 

 gray crystalline and associated reddish gray compact limestone 

 pebbles is that they contain a Trenton fauna, with a strong Low- 

 ville and Black river element, and that, on this account, they evi- 

 dently must be placed within the lowest Trenton; a conclusion 

 which seems to be strengthened by the presence of a number of 

 forms of lower Trenton occurrence, and the fact that the great 

 majority of all forms observed range from the Lowville to the 



