Solitary Ascidian or Tunicate (Class Ascidiacea)
Their name comes from the Greek 'askidion' which means 'leather wine bag'.
Hence their other name 'tunicate' from the leathery 'tunic' of their outer skin.
Essentially, they are a hollow sack made of tough leathery tissue, with two openings.
The creature creates a current through these openings, passing water through
an internal filter which traps minute edible titbits.