As it doesn't look like I'll be able to get out to collect today, I thought I'd throw the ol' shoulder into some basic prep, and this one presents a few challenges.
I did manage to find two full Flexicalymene senaria prones in Brechin, but lost one in the field (doh!). This one is pretty kinked up, almost as though a cartoon iron bar was dropped on its thorax. So, it undulates and stretches accordingly, and it is unclear just how much of it is tucked in the matrix.
The first pic is pretty much how I found it.