Description

Worm-shaped shells are among the most confusing to identify. Three gastropod families among the Cerithioidea superfamily make coiled shells much like the tube-building annelid worms. Proper identification of these shells has often been confounded by different authorities, but Keen, 1958 notes that the shells of the annelid worms can be clearly distinguished from those of the Cerithioidea gastropods; i.e., the annelid shells are two-layered and dull inside, whereas the gastropod shells are three-layered, having a  glossy deposit of nacre on the inside --a clear identifier. 

 

The Vermetidae shell shown opposite, Serpulorbis (Aletes, syn.) squamigerus, is a California shell. Unlike Aletes semiquadrus, it does not have an operculum. Most  Vermetidae  gastropods grow in irregular masses --often even more irregular than shown in the particular specimen  pictured here. They generally live inside sponges, and below the littoral zone. 

 

The worm shell shown at lower right, Vermicularia fargoi, belongs to the Turritellidae family. It is  distinctively different from most Turritellidae in that the whorls begain to separate as it grows. The shell pictured here, V. fargoi, is distinguished by a tightly coiled region that is 3 cm long; V. spirata, which is otherwise similar, would have a tightly coiled region half that length. Many of the Turitellidae shells actually show a changed plane of coiling after the first few whorls, such that the spire might end up at a right angle with respect to the later coils. This characteristic easily confounds a correct identification, mistaking it for a Vermetidae shell.

 

Classification

Class: Gastropoda

Clade: Sorbeconcha

Superfamily: Cerithioidea

 

Major Families & Genera

Family: Turritellidae

• Genus: Vermicularia

Family: Siliquariidae

• Genus: Siliquaria

Family: Vermetidae

• Genus: Aletes
• Genus: Bivonia
• Genus: Petaloconchus
• Genus: Serpulorbis
• Genus: Trypsycha

Vermicularia fargoi (Olsson, 1951)
Fargo's Worm Shell
Family: Turritellidae
(a 6.5 cm specimen)