The Camouflaged Fossil

So I am out in the field and picking up limestone plates that contain sections of Archimedes bryozoan like the one shown in this picture.  One hopes to find Fenestella attached to the outer grove edges of the Archimedes that will be preserved in the plate. For the most part, it is just the screw part that is found.
This posting is about camouflaged fossils and when this limestone plate gets wet, it reveals the presence of a white crinoid arm. Not sure of the crinoid's identity but it was surprise when it was cleaned. Last image shows plate with ruler to give one some idea of its size.
The lesson I take away from this, is sometimes things are not as they first appear.