TUEXTON CONGLOMERATE OF UYSEDOKPH IIIT.L 99 



r e n s s e 1 a e r i c a are slightly differing ea«sterii representa- 

 tives of western Lowville limestone forms, while Enrychilina 

 reticulata is known only from the Lowyille and Black river 

 limestones^. 



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 - 

 n e s q u i n a d e 1 1 o i d e a , reported from the Trenton of New 

 York, Canada and the west; Triple ci a nucleus, Car- 

 ina r o p s i s c a r i n a t a , L i o s p i r a s u b t i 1 i s t r i a t a , 

 P t e r y g o m e t o p u s e b o r a c e u us . D a 1 m a H: 1 1 e s 

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

 stone ; Leptaena rhomboidalis and B y t h o c y p r i s 

 c y 1 i n d r i c a , w^hlch begin in the Trenton and extend upward. 

 Of these R a f i n e s q u i n a d e 1 t o i d e a is only weakly 

 represented by a form showing certain yarietal 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 ; T r i p 1 e c i a nucleus, C a r i n a r o p s i s 

 carinata, Liospira subtilistriata and P t e r y ■ 

 gometopus eboraceus are not reported from extra- 

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

 Lowyille and Black riyer faunas are rather meager, and haye 

 been thoroughly inyestigated in but a few localities, they may 

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

 able in the case of Liospira subtilistriata, which 

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

 ton limestone at Watertown ; but as T r i p 1 e c i a nucleus, 

 C a r i n a r o p s i s carinata and Liospira subtili- 

 striata are characteristically doveloped and coninion 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 indicatiye of the Trenton age of the gray lime- 

 stone. Pterygometopus eboraceus has thus far 



* 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 XJlrich as specifically If not generically different. 



