Zygospira erratica

Zygospira erratica. These two are set on a limestone hash plate with an orthocone to the left. Both are the same species and have an obvious sulcus. Mimico creek, Toronto, late Ordovician, Georgian Bay formation.
Edit: I also have found a massive slab of limestone that had a death assemblage of these brachiopods . I forgot to take photos though , and I'm not sure if the slab is still there.