100 NEW YORK STATE MUSEUM 



been foinul <mly in one specimen in the Trenton of Saratoga 

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

 D a 1 ni a n i t e s achates, T. e p t a e n a r h o m b o i d a 1 i s 

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

 bution, niusl be c(Mi**idered as stnni«;ly su]»porlin}- the yiew o-f 

 the Trenton aj:e of thi** fauna. su«:jresled by the fossils just named. 

 In weijihin^ the evidence furnished by the two jrroups 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 larjrely 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 fron. 

 the conglomerate bed of Rysedorph hill, however, show, with tJie 

 exception of E u r y c h i 1 i n a r e t i c u 1 a t a , 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 .hie 

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

 stone of New York have not yet been thoroughly collected and 

 • studied, and partly due to the smallness of the fauna known as 

 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 

 ])ebbles 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 numljer of 

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

 majority «»f all forms observed range from the IvOwville to the 



