Panorama (4 images) of tissue section across top of medusoid

 

 This image shows the tissue across the region of the top of the ampulla that had been decalcifying, prior to liberation of the medusoid.  

 

The following section was cut across what I think is the Velar Plate, which will open up to leave a velum around the periphery of the medusoid, allowing propulsion and escape.