The hinge line area is missing from this cast but the shape indicates it could be a Ctenodonta nastua.
I think this is a Modiolopsis type pelecypod, possibly Modiolopsis ovata.
I think this is another species of Ctenodonta called C. levata.
Along with the typical straight shelled Cephalopods you occasionally can find one with a wavy shell.
This is likely a Spyroceras but there is not enough to be positive.
All the specimens shown were collected from the Verulam formation which is middle Ordovician in age (Katian/Mohawkian stage). I base my ID's on the book "South-Central Ontario Fossils" by William Hessin.