270 B. K. Emerson — " Bernarclston Series " of 



the limestone, but found mingled in the crunched schist frag- 

 ments of the chloritic rock, which lies below the limestone 

 and is exposed in the bluff to the north. At a later date I had 

 further excavation made, uncovering the northern bluff where 

 also the mica schist approached the limestone at its northern 

 end, and I exposed here a zigzag fault line between the schist 

 on the west and the black, magnetite-pyrite-chlorite-limestone, 

 and below this with the white limestone itself, e on map, fig. 2. 

 The fault plane is nearly vertical. The relation of the beds at 

 this point are made plain by fig. 5. This latter excavation was 

 made by direction of the United States Geological Survey. 



f. The Limestone. — The limestone which forms the center of 

 interest of the section, is exposed in many old pits, extending 

 from the bluff overlooking the brook, to the largest opening 

 overhung by birches, where the rock is most fossiliferous ; and 

 the line of outcrops is continued, by more scattered openings, 

 farther southwest. It extends in all about 125 m. from 

 northeast to southwest, that is along the line of strike. It is 

 for the most part a coarsely crystalline, saccharoidal limestone, 

 at times so coarse that cleavage pieces of calcite 8 centimeters 

 across can be obtained from it. Below it is in thick beds with 

 stratification mostly obliterated, while the upper portion, for 

 about 2 meters, is thin-bedded, finer grained and micaceous. 

 The rock contains some pyrite, which with the more abundant 

 deposit of the same in the bottom of the quartzite, has been 

 the source of the great amount of porous limonite, which fills 

 broad veins and great cavernous spaces in the limestone. Its 

 modern formation is attested by the rootlets changed into 

 limonite enclosed in it. 



It makes a strange impression to turn over a mass of coarsely 

 crystalline limestone, and find the weathered surface covered 

 with Crinoid stems or Corals. In masses showing no trace of 

 fossils, these are brought out equally well in thin sections ; and 

 I have even observed a fragment of the shell of a Terebratula, 

 preserving the punctate structure, the pores agreeing closely 

 in position and measurement with those of modern genera. 



In the section fig. 4 all the fossils known are assigned to 

 their proper horizon so far as known to me. I would especially 

 note the fact, to which my attention was first called by Pro- 

 fessor J. M. Clarke, that the line of division between the two 

 paleontological horizons represented falls well down in the 

 limestone, and that the upper meter of the latter is thin bedded 

 and wants the forms found below, while it carries the peculiar 

 annulate crinoid stems found also very abundantly in the 

 quartzite above. 



The shaly limestone is in places much fissured and cemented 

 at times with veins 5-10 mm wide of a completely granitoid 



