SILURIAN 





Locally considerable masses of the limestone have been altered to calcite. 

 While strike and dip can generally be made out and appear to conform to 

 anticlinal structure, occasionally the bedding is entirely obliterated. 



MIDDLE SILVRIAy FAUNA 



The magnesian limestones of the Lower Eamparts on the Porcupine 

 river are characterized by a ^liddle Silurian fauna closely related to tlie 

 Xiagara fauna of the central LTnited States, as well as to the cosmopolitan 

 fauna (Silurian) of Europe and Asia. The character of this fauna i>: 

 shown by the following list of species, which were obtained from the 

 north bank of the Porcupine about 5 miles above the entrance to the 

 Lower Eamparts : 



Silurian Fossils from the Lower Ramparts, Porcupine River. 



Lichenaria cf. concentrica Hall. Camarotoechia negJecta Hall. 



Favosites cf. favosus Goldf. Rhynchotreta cuneata Dalm. var. 



Cohimnaria sp. Atrypa reticularis (Linn.). 



Alveolites sp. Atrypa cf. calvini Nettlerotli. 



DipliyphyUum sp. Atrypina n. sp. 



Zaphrentis 1 sp. Cwlospira cf. clintoni. 



Stropheodonta sp. Reticularia cf. proxima Kindle. 



Strophonclla cf. macra M. and W. Spirifer noiilis Barr. 



Leptwna rhomboidalis (Wilckens). Nucleospira pisiformis Hall. 



Leptwna cf. quinquecostata McCoy. Meristina nitida Hall. 



Lcptwita n. sp. Meristina sp. 



Strcptis greyi Davidson. Meristella 1 cf. suhuinhita McCoy. 



Dalmanella cf. elegantula (Dalman). Strophostylus sp. 



Anastropliia cf. Tjrevirostris (Sow. ?) Cypricardinia arata Hall. 



Hall. Cyrpicardinia n. sp. 



Striclclandinia sp. Illwnus ai-matus Hall. 



Pentiimcrus ohlongus (Sow.). Spliwrexochus cf. romingeri Hall. 



Cloriiida VinguUfera (Sow.). Eiicrinurus sp. 



Camarotcechia cf. borealis (Sclil.). Prostus, sp. 

 Camarotoechia sp. 



QRAPTOLITE FAUNA 



An exposure near the upper end of the Eamparts indicates the charac- 

 ter of the beds near the top of the Silurian series, where shales, which are 

 rare lower in the series, are conspicuous. The beds observed here are 



shown below : 



Section near upper End of Ramparts. 



Feet 



Black shale and Mack to dark gray dolomitic and silicoons limestonp T40 



Hard siliceous black limestone 12 



Black and gray fissile shale interl)edded *>'* 



Dolomitic limestone weathering huff, mostly gray on fresh fracture 100 



