23 



tinuous layer of calcareous concretions, one-half foot below 

 the top at the upper end and one foot below the top at the 

 southern end. This layer, therefore, dips to the south at a 

 higher angle than does the Styliolina bed. It corresponds 

 to the lower of the two layers of concretions noticed in 

 Section 2, the shale over it containing the Schizobolus fauna. 

 In the shale beneath the concretions, a considerable variety 

 of fossils occur, most of which, however, are but sparingly 

 represented. The characteristic Hamilton trilobite Phacops 

 rana (Green) is not uncommon, while a minute pteropod, 

 the Tentaculites gracilistriatus (Hall) occurs in great abund- 

 ance in a layer less than half an inch think. This species 

 occurs by the hundreds on the shale laminae, closely re- 

 sembling the Styliolina fissurella (Hall), and showing a 

 similar longitudinal line of compression. The concentric 

 rings or annulations, however, which are characteristic of 

 the genus, serve to distinguish it at once. Spirifer tullius 

 (Hall) is also a frequent and characteristic fossil. 



Just beyond the lower end of the section, in the bed of the 

 stream, appears a small anticlinal fold, the axis of which 

 extends nearly north and south. The fold indicates a lateral 

 compression of the strata, as a result of which they were 

 crushed and uplifted. The line of weakness thus produced 

 probably determined the course of erosion, which has re- 

 moved the overlying rock. In the shale thus crushed occur 

 a large number of the spiny brachiopod Productella spinu- 

 licosta (Hall), none of which, however, retain their original 

 outline. The long slender curved spines appear, however, in 

 great numbers on the shale, an occurrence nowhere else 

 observed. (Fig. 112, Pt. II. ). 



Section 4 (E). 



Plate VII. 



This section is cut into the left bank of the stream, begin- 

 ning opposite the southern end of Section 3, and extending 

 in a general north-west direction. Opposite it is the deepest 



