Tubiluchidae
Tubiluchidae is one of the two families of priapulimorphidan priapulid worms. Taxa 
The family includes only the genus Tubiluchus van der Land 1968, and in some classifications Meiopriapulus. A full list of the included species:

Anatomy 
The Polythyridium is a gut component. References 

Priapulida
Ecdysozoa families