Rafinesquina alternata and Sowerbyella sericea brachiopods from the Whitby formation

This slab is a two for one in terms of species present. It has an example of Rafinesquina alternata as well as Sowerbyella sericea. It's from the Collingswood member of the Whitby formation. These are both uncommon fossils to find in the Collingswood member and could be washed in from another location by a storm as black shales generally represent anoxic, deeper water conditions.

Overview of the slab

Rafinesquina alternata

Sowerbyella sericea

The Whitby formation is Ordovician in age (late Ordovician, Katian/Mohawkian stage).
These 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. 125-126, 128 to help identify these fossils.