25 



end of the section. The lowest portion of this mass of shale 

 contains chiefly Ambocoelia praeumbona (Hall), which for 

 the first time made its appearance in this region, and con- 

 tinued to the close of the Hamilton or Mesodevonian period. 

 The characteristic species of this fauna all occur in these 

 shales, the type species Spirifer tullius ( Hall ) having its best 

 development near the middle of the series. The layer of con- 

 cretions which marks the downward limit of the Schizobolus 

 sub-fauna (faunule), appears again in this section. It is 

 usually double, and very continuous. At the upper end of 

 the section it is twelve inches below the Styliolina limestone, 

 while at the lower end it is only four inches below that rock. 

 The point of first appearance of this layer in Section 4 is just 

 opposite the southern end of Section 3. In both places the 

 layer is a foot below the Styliolina band, and approaches it 

 as we go northward. 



The shale between this layer and the Styliolina limestone 

 is especially rich in Liorhynchus multicostus (Hall), which 

 occurs by the hundreds between certain of the shale laminae. 

 Many of the specimens are of great size, but the shell com- 

 monly breaks away, while the specimens usually present a 

 compressed, semi-enished appearance. The other members of 

 the Schizobolus sub-fauna are by no means rare. The layer 

 of pyrite nodules noticed in Section 2 is sparingly repre- 

 sented here, occuring in a similar position. 



At the lower end of the section the Genesee shales form the 

 top of the bank, which is here much lower than elsewhere. 

 Beyond the end of the section, where a roadway leads to the 

 top of the bank, is the mouth of "Fern brook " ravine, which 

 is cut back nearly to the main road, and terminates in a 

 vertical wall, over which, in wet weather, the drainage of a 

 considerable portion of country descends as a fall. In this 

 ravine only the Upper Devonian shales are exposed, and it 

 is a place more frequented by the botanist than by the 

 geologist. 



