What is "saccoglossus"

Saccoglossus is a genus of acorn worm (Class Enteropneusta). It is the largest genus in this class, with 18 species.

This genus is characterized especially by the concentric rings of muscle fibers in the proboscis. Many Saccoglossus can be found in coastal mud and sand habitat, often near bays. They dig tubes in the substrate, ejecting conical piles of castings in a spiral fashion.

Acorn worms of this genus are known for the production and accumulation of various halogenated phenols and pyrroles.