150 NEW YORK STAT© MUSEUM 



Rhynckotrema inequivalve Castelnaw 



Parastrophia heiniplicata Hall 



Hormospira alexandra Billings 



Liospira americana Billings 



Murchisonia ?? 



Sponge 

 Iso. 2 Strophomena incurvata Shepard 



Parastrophia hemiplicata Hall 

 Iso. 1 Strophomena incurvata Shepard 



Mr Van Ingen regards the fauna as being that of the lower part 

 of the Trenton as found in the Chainplain valley. 



Layer no. 4 is a most remarkable rock, being a limestone but 

 containing large quantities of quartz sand, and in places large 

 pebbles of the old crystallines. The sand under the microscope 

 is mostly well rounded and abraded, but some grains are angular. 

 A little plagioclase feldspar is present, and one zircon was de- 

 tected. In size the fragments range from .1 mm up to 15 mm 

 (.004 to .5 inches). Definite iron-bearing silicates are lacking, but 

 one magnetite fragment was observed. Thin sections were cut 

 of two pebbles of the crystalline rock. Each was found to contain 

 quartz and kaolinized microperthite in about equal amounts, and 

 to have many pyrites disseminated through it. The pyrite was 

 in part altered to limonite. The pebbles were certainly derived 

 from the ancient crystallines and are pyritous quartzites or 

 gneisses such as accompany the crystalline limestones. One 

 pebble of a very fine limestone was also examined microscopically, 

 but showed nothing unusual. 



Utica slate. The Utica appears in three small separate ex- 

 posures, lying on the west side of the river. The northern one 

 is the largest and best, being 100 feet long, and 13 feet thick. 

 The slaty cleavage strikes n 52 e, 15 n w, referred to the true 

 north. Bedding is not apparent. In the two southern localities 

 only a foot or two of weathered slate was exposed. The large 

 outcrop was divided into five sections, of which the upper was 3 

 feet, the other four 2 feet each, and the fossils from each were 



