Dec, 1912.] Ordovician Section, Lake Huron Area. 45 



In Ohio, Whiteavesia pholadiformis and Modiolopsis concentrica 

 come in at the base of the Fort Ancient division of the Waynesville 

 bed, and continue to the top of the Waynesville, but they are 

 represented by at least very similar forms even in the Liberty. 

 Under these circumstances it was natural at first to regard these 

 strata, on Manitoulin, which carry the Whiteavesia pholadiformis 

 and Modiolopsis concentrica fauna as Richmond. However, the 

 bryozoans submitted to Dr. Ulrich tell a very different story, and, 

 until further evidence has been accumulated, it is regarded wiser 

 to remove them from the Richmond column. For collecting 

 purposes these beds are well exposed for a distance of about two 

 miles along the shore between Wekwemikongsing and the Rich- 

 mond Clay Cliffs on the eastern side of Cape Smyth. The total 

 thickness of the Wekwemikongsing section on Manitoulin island 

 may equal 100 feet in the Cape Smyth area. 



8. Richmond Strata on Manitoulin Island. 



C. Waynesville Beds, or Lower Richmond. 



Overlying the Wekwemikongsing beds, with their Lorraine fauna, 

 is a series of interbedded limestones and clay shales of undoubted 

 Richmond age. At the base of these undoubted Richmond beds, 

 Hebertella insculpta, frequently associated with Catazyga headi, 

 is almost invariably present, and since Hebertella insculpta and 

 Catazyga headi, on Manitoulin, are limited to the basal part 

 of these beds, both fossils here serve as valuable diagnostic 

 fossils. Associated with these fossils in the same layers occur: 

 Streptelasma rusticum, Columnaria alveolata, Protarea papillata, 

 Rhombotrypa quadrata, Hebertella occidentalis, Platystrophia clarks- 

 villensis, Strophomena huronensis, Rafinesquina alternata very fiat 

 fomi, Plectambonites sericea, Rhynchotrema perlamcllosa, Zygospira 

 modesta, Cyclonema bilix, and Pterinea demissa. These associated 

 fossils, however, are not confined to the Hebertella insculpta and 

 Catazyga headi horizon but range upward for variable distances 

 into the overlying Richmond. 



The lower part of the Richmond, on Manitoulin, is by far the 

 richest in fossil remains, and many species, especially among the 

 brachiopoda, appear to be confined to this lower part. Between 

 Gore Bay, Kagawong, and Little Current, a conspicuous coral 

 reef, from one to three feet thick, containing Columnaria alveolata 

 and Calapoecia huronensis, frequently is found between 35 and 45 

 feet above the base of the Hebertella insculpta horizon. It has 

 been found that while most of the fossils which begin their range 

 at or near the Hebertella insculpta horizon reach the Columnaria 

 reef horizon, many of these species do not extend their range 

 beyond this reef. Among the latter may be mentioned : Protarea 

 papillata, ConsteUaria polystomella, Rhombotrypa quadrata. Crania 

 scabiosa, Rafinesquina very flat form, Plectambonites sericea. 



