Worm Snail (Scale Worm Snail)
Phylum: Mollusca, Class: Gastropoda, Order: Littorinimorpha, Family: Vermetidae, Genus: Thylacodes, Species: T. squamigerus · Vermetidae (Worm snail family) · Gastropod; irregular tubular/worm-like shape. Currently a fragment of a larger colony.
Species
Thylacodes squamigerus (formerly Serpulorbis squamigerus)
Shell Type
Gastropod; irregular tubular/worm-like shape. Currently a fragment of a larger colony.
Family
Vermetidae (Worm snail family)
Size
The fragment is approximately 0.75 to 1 inch in length; the diameter of the tube is about 0.3 inches. Adults in colonies can reach several inches long.
Color & Pattern
Dirty white to grayish-tan exterior with brownish staining. Surface is characterized by many small longitudinal ribs and transverse growth scales. Interior is smooth, glossy, and porcelain-white.
Rarity
Common. They are frequently found as broken segments on beaches or as encrustations on larger rocks near Cabo.
Habitat
Found in the intertidal and shallow subtidal zones, typically attached to rocks, pier pilings, or other shells. They form dense, reef-like colonies in areas with moderate wave action.
Geographic Range
Eastern Pacific: common from Central California south to the Gulf of California and Cabo San Lucas, Mexico.
Description
An unusual gastropod that resembles a tube-worm. Unlike most snails, it does not have a coiled shell as an adult; instead, it grows an irregular, calcareous tube cemented to a hard substrate. The exterior is rugose and scaly, while the interior remains highly polished.
Key Features
Distinguished by its irregular tubular growth, lack of an operculum (unlike Serpulidae worms), and the presence of longitudinal ribs covered in fine scales.
Collector Value
Minimal financial value (less than $1). It is primarily of educational interest or valued as a curiosity for collectors focusing on unusual molluscan growth forms.
Condition Notes
Fair. This is a weathered beach fragment representing a section of the tube. The apical end and the attachment base are missing. No periostracum remains; the shell shows some erosion from sand tumbling.
Interesting Facts
These snails are sessile filter feeders. They cast out a net of sticky mucus from their pedal gland to trap plankton and detritus, then 'reel' the mucus net back in with their radula to eat it.
Ecological Role
Important reef-builders in certain Pacific environments. They serve as filter feeders that clean the water and provide architectural complexity as habitat for small invertebrates and algae.
Similar Species
Petaloconchus montereyensis (smaller, more tightly coiled) and various Serpulid polychaete worms (which have different tube structures and lack the molluscan radula and scales).
Beach Finding Tips
Look in tide pools or among rocky outcrops at low tide, especially near the base of cliffs in Cabo. Look for clusters of 'stony worms' cemented to the undersides of rocks.
Notes
Cabo