CAMBRIAN OF NORTH ATTLEBORO. 391 



west of locality 1, in the underbrush, and about halfway between locali- 

 ties 1 and 2 on the west side of the set of exposures already described. 

 The temptation is very strong to consider the quartzite and the associated 

 green shales as forming the lowest beds of the series actually exposed. 

 The limestone beds immediately toward the east of the green shale and 

 associated quartzite layers^ containing Hyolithes and Hyolithellus chiefly, 

 at locality 1, and again just east of the green shales and sandstones halfway 

 between localities 1 and 2, could then be considered as forming an immedi- 

 ately overlying horizon^ while the beds still farther eastward, containing 

 frequent trilobite remains {Agraulus strenuus), might be considered as 

 belonging to a still higher horizon. This would suggest that locality 2 

 belongs to a horizon slightly higher than locality 1. 



About 700 feet north of locality 2 is found a granite boss, the northern 

 margin of which extends northeastward, forming a steep wall. On the 

 northern side of this wall, in close contact with the granite, a small exposure 

 of red shales was unearthed in 1887. 



Red shales also occur at various points on the eastern side of the valley 

 in which localities 1 and 2 occur. The general conclusion is that the val- 

 ley as far as described is underlain altogether by Olenellus Cambrian rocks. 



The western side of the valley is bordered by the Hoppin Hill granite 

 boss. On the northeastern side, toward North Attleboro, occurs the second 

 boss, already described, and along the remainder of the eastern side of the 

 valley the Olenellus Cambrian is overlain by the Carboniferous. The most 

 southern Carboniferous exposure north of the east-west Hoppin Hill road 

 and east of the Cambrian area, strike N. 10^ W., dip vertical, occurs on 

 the hillside, only 326 feet north of the road leading east down from Hoppin 

 Hill. Another exposure is 250 feet north; a third is 115 feet north, strike 

 N. 40^ E,; a fourth is 75 feet north, strike N. 15^ E., dip steep west. All 

 of these exposures are conglomerates, in which the pebbles consist of a hard 

 glassy quartzite. 



South of the Hoppin Hill road leading eastward are several additional 

 exposures of Carboniferous conglomerate and shale on the east side of the 

 Olenellus Cambrian valley. 



The construction of the new railroad through the western part of the 

 village of North Attleboro has disclosed a series of red shales south of 

 the depot, as far as the bend of the road toward the southeast. The 



