Prossek and Cuminus— Lower Silurian Sections. 



623 



9. Zygospira recurvirosira, Hall. (c) 



10. Betterophon bilobatus (Sowerby). (r) 



11. Asaphus platyeephaht,s, Stokes. (c) 



12. CalymeHfi callicephala, Green. = G. senaria, Con. (c) 



13. C&rav/rus plem'exanthemus, Green (?). (r) 



This zone includes Nos. 8, 5> and 10, of White, the combined thickness of 

 which is twelve feet, the same as that in the present section. (Plate III.) 



A 4 . A stratum of massive dark blue limestone conspicuous in 3 ^? e | 9 

 the side of the gorge along the path above Sherman fall, varying in thickness 

 from two feet, seven inches, to two feet, ten inches, called for convenience 

 in the general section, three feet. On weathering, the stratum splits into thin 

 irregular layers similar to those immediately above and below. This promi- 

 nent stratum is a convenient stratigraphic mark for this part of the section 

 and is clearly shown in Figure A Plate IV, of White's article, where it is 

 described as D 11 of his section. 



A 5 . The heavy blue stratum may be readily followed to the foot 7^^%^ 

 of the lower fall of High fall, and A 5 includes the rocks from the top of 

 this layer to the base of a conspicuously contorted stratum opposite the top 

 of the lower fall of High fall. The rocks are thin and shaly in the upper 

 part with thicker layers in the lower part. 



.1". From the base of the contorted stratum to the crest of the :>1 F l e \ 77 

 upper part of High fall. The folded stratum is well shown in Figure A, 

 Plate III, of Mr. White's article. The rocks are thin-bedded. Both the 

 lower and upper portions of High fall, or zones A 5 and A of this 

 section, are shown in the accompanying plate (TV). The following species 

 were collected in A 6 : 



1. 



MonticulApora (Prasopora) l/ycop&rdon (Say); 



(c) 





Stictopora, sp. 





3. 



Rafoiesquina <l<H<>i<l<a (Con.), H. and C. 



(aa) 



4. 



Orthis QPlat/ys1/rophid) biforata (Schl.), Pill. 



(*) 



5. 



Orthis (^Dalmanella) testmdina/ria, Dal. 



(aa) 



6. 



Plectambonites sericea (Sowb.), II. and C. 



(aa) 



7. 



Tellinomya <IuLi<t, Hall. 



0) 



8. 



Wndoceras proteiforme, Hall. 



(c) 



9. 



Cyrtoceras, sp. 



(r) 



10. 



AsapJ/ us platyoephal us, Stokes. 



(aa) 



11. 



Crinoid segments. 





