TRENTON CONGLOMERATE OP RYSE>DORPH HILL 33 



Liospira subtilistriata Hall sp. 



Pleurotomaria subtilistriata Hall. Pal. N. Y. 

 1847. 1:172 



This characteristic small, lenticular gastropod' was found in 

 great abundance in the gray limestone pebbles of Rysedorph hill. 

 At the time of the publication of the first volume of the Paleon- 

 tology of New York Hall knew this species only from the concre- 

 tionary limestone near the base of the Trenton at Watertown. 

 Dr White did not observe it in the Trenton Falls section and the 

 other localities along the West Canada creek, nor. has he reported 

 it yet from the Lake Ohamplain region. As it is mentioned 

 neither by Ulrich and Scofield from Minnesota and the western 

 states nor by Dr Whiteaves from Lake Winnipeg, nor by Schu- 

 chert from Baffin Land, it is evidently a form of horizontally and 

 vertically restricted distribution and quite probably of some 

 taxonomic value, indicating a low Trenton horizon. (Group 7) 



clathrospira Ulrich & Scofield 



Clathrospira subconica Hall sp. 



Pleurotomaria subconica Hall. Pal. N. Y. 1847. 

 1:174 



A few small specimens showing the characteristics of this 

 species well developed were obtained in the gray crystalline lime- 

 stone pebbles. Hall, in describing the species, had specimens 

 from the lower part of the Trenton limestone at Watertown and 

 from the Lorraine shales at Turin and Pulaski. In Canada it 

 occurs also in the Black river beds, and in the west it is found 

 in the Stones river group. 



Ulrich and Scoifield have described a very similar western form, 

 C. conica, which is considerably smaller than C. sub- 

 conica, and hence is said to have often been confused with 

 young specimens of that species. The specimens from Ryse- 

 dorph hill, though also much smaller than the average specimens 

 of C. subconica, failed to agree with C. conica in other 

 differentials from C. subconica. (Group 7) 



