TRENTON CONGLOMERATE OF RYSEDORPH HILL 99 



rensselaeric a are slightly differing eastern representa- 

 tives of western Lowville limestone forms, while E u r y c h i 1 i n a 

 r e t i c u 1 a t a is known only from the Lowville and Black river 

 limestones 1 . 



There are, on the other hand, a number of forms which combat 

 a conclusion based on the evidence just cited. These are: R a f i - 

 nesquina deltoidea, reported from the Trenton of New 

 York, Canada and the west; Triplecia nucleus, Car- 

 inaropsis carinata, Liospira s u b t i 1 i s t r i a t a , 

 Pterygometopus eboraceus, D a 1 m a n i t e s 

 achates, which are as yet known only from the Trenton lime- 

 stone; Leptaena r h o m b o i d a 1 i s and B y t h o c yp r i s 

 cylindrica, which begin in the Trenton and extend upward. 

 Of these Rafinesquina deltoidea is only weakly 

 represented by a form showing certain varietal differences! in the 

 suppression of the intermediate finer striae and concentric wrin- 

 kles on the disk, and is therefore probably not to be relied on 

 as a safe indicator of the taxonomic relations of the beds under 

 consideration ; Triplecia nucleus, C a r i n a r o p s i s 

 carinata, Liospira s u b t i 1 i striata and Ptery- 

 gometopus eboraceus are not reported from extra- 

 limital localities, and, considering the fact that in New York the 

 Lowville and Black river faunas are rather meager, and have 

 been thoroughly investigated in but a few localities, they may 

 possibly go below the Trenton limestone. This is specially prob- 

 able in the case of Liospira s u b t i 1 i s t r i a t a , which 

 is reported by Hall as occurring only near the base of the Tren- 

 ton limestone at Watertown; but as Triplecia nucleus, 

 Carinaropsis carinata and! L i o s p i r a s u b t i 1 i - 

 striata are characteristically developed and common in the 

 limestone pebbles, they must be considered as important factors 

 of the fauna of the latter and, with our present knowledge of 

 their ranges, as indicative of the Trenton age of the gray lime- 

 stone. Pterygometopus eboraceus has thus far 



1 The specimen from the Onondaga chert of New York referred by Jones (Quar. jour. geol. soc* 

 1890. 46; 593) to this species is considered by Ulrieh as specifically if not generically diff event* 



