Annelid? From Georgian Bay formation, GTA

[FluffUnicorn]

I found this fossil in the Georgian bay formation in the GTA in southern Ontario. I have no idea what the area highlighted in blue is (first picture). It looks like a slug or some type of annelid. My only guess is some type of Machaeridian, but I doubt it's that as well. Any ideas? 

It measures around 9 cm tip to tip, 

Thanks

[connorp]

Definitely not an annelid. Could be part of a coral.

[FluffUnicorn]

Yeah I think you’re right, I’m not good with corals from this time period but it doesn’t seem like a standard rugose coral. After some more research, it looks a bit like a conulariida, but I’m not sure.

[Rockwood]

1 hour ago, FluffUnicorn said:

, it looks a bit like a conulariida, but I’m not sure.

I'd put the odds about even with it being the remnant of more nautiloid shell. The shell seems to thin nearer the living chamber in most, I believe. That would leave both with about the same preservation potential relative to the nautiloid seen.

I think. 

[Tidgy's Dad]

I say geological / erosional.