Upper Ordovician bivalve ID -- Cymatonota?

[Rogue Embryo]

Found this lovely pair of bivalves in Mimico Creek over the weekend and hoping to get some help on ID. It looks like either Colpomya or Cymatonota, based on images I've seen. Any ideas in this?

 

Camille

[Tidgy's Dad]

I think Cymatonota is more elongated than these specimens, so I'll go with Colpomya faba or maybe Modiolopsis ovata.  

[Misha]

Those are some very nice fossils!

[Rogue Embryo]

Hi, @Tidgy's Dad, this is very helpful! I'm going to go provisionally with Colpomya, though I haven't seen enough of these to say with much confidence. This is a good starting point for me to learn more. I'm determined to finally get a copy of Hessin's big book.

 

And thanks, @Misha!

 

Camille

[Tidgy's Dad]

1 hour ago, Rogue Embryo said:

Hi, @Tidgy's Dad, this is very helpful! I'm going to go provisionally with Colpomya, though I haven't seen enough of these to say with much confidence. This is a good starting point for me to learn more. I'm determined to finally get a copy of Hessin's big book.

Hessin is very, very useful, though he doesn't cover the Georgian Bay Formation in as much depth as he does other Ordovician formations in the area.