A closeup and stacked image of a green tree frog's eye. Anstead, QLD.
Snail, I think you are missing some shell. Apparently some slugs have shell remnants partially or completely embedded beneath the skin. These are known as slugs because slugs are basically snails without a shell (they can hide in).
I found whole colonies of these insects in curled leaves of my ornamental ficus. I thought it was just a disease until I investigated inside one of the newly curling leaves. In this image you can see hatched eggs, nymphs and winged adults.