I've found a couple of examples of small Cephalopods in the Collingswood member of the Whitby formation. They are hard to photograph as they do not contrast much with the black shale but I can see they are conical in shape and taper to a point. Some examples have fine ribbing or striations parallel to the shell growth. According to William Hessin these are likely Geisonoceras tenuistriatum which is restricted to the Whitby formation.
The Whitby formation is Ordovician in age (late Ordovician, Katian/Mohawkian stage).
fossils were collected from the St. Mary's Limestone Quarry in
Bowmanville, Ontario. I used William Hessin's book "South Central
Ontario Fossils", 2009, Self Published, pg. 155 to help identify these