What is "thylacodes"

Thylacodes is a genus of sea snails, marine gastropod mollusks in the family Vermetidae, the worm snails or worm shells. The species in this genus were previously placed in the genus Serpulorbis.

Unlike some other vermetids, the species in this genus have no operculum.

Like other vermetids, the species in this genus do not have regular shell coiling like that of a typical gastropod shell, instead they have shells which are irregular. They are usually cemented onto a hard surface. Because of all this, the shells resemble the calcareous tubes of worms in the polychaete family Serpulidae.