Screw Shell, Great Screw Shell, Awl Shell
Phylum: Mollusca, Class: Gastropoda, Order: Littorinimorpha, Family: Turritellidae, Genus: Turritella, Species: Turritella terebra · Turritellidae (Screw Shell family) · Gastropod (univalve); Spiral/Auger-shaped. This is a whole shell specimen.
Species
Turritella terebra
Shell Type
Gastropod (univalve); Spiral/Auger-shaped. This is a whole shell specimen.
Family
Turritellidae (Screw Shell family)
Size
Approximately 2.5 - 3 inches (65-75mm). This is a mid-sized juvenile or sub-adult; the species can reach up to 6 inches (150mm).
Color & Pattern
Uniform light tan to brownish-grey base with darker bands in the sutures. The coloration appears naturally weathered but retains its subtle gradient. No distinct spots are present, and the periostracum is mostly missing, revealing the matte calcareous surface.
Rarity
Common; frequently found washed up on beaches in Southeast Asia and the tropical Pacific.
Habitat
Subtidal marine environment; typically found in soft muddy or sandy substrates at depths of 10 to 50 meters.
Geographic Range
Indo-West Pacific region, ranging from the Red Sea and East Africa to Australia and the Philippines.
Description
An elegant, highly elongated spiral shell consisting of numerous rounded whorls. The sculpture is characterized by fine spiral ridges (striae) that run parallel to the sutures. The shell tapers to a sharp, slender point (apex) and lacks a siphonal canal or distinct umbilicus. Its structure is solid yet appears delicate due to its slender profile.
Key Features
Tightly coiled whorls, very high spire with a small, circular aperture. Distinctive 'screw' thread appearance with deep sutures between whorls and fine spiral ribbing.
Collector Value
Relatively low commercial value ($1-$5) due to its abundance, but highly desirable for decorative displays and educational collections because of its perfect geometric spiral.
Condition Notes
Good condition. The apex (tip) appears mostly intact, which is rare for beach-found specimens. The outer lip is not clearly visible but usually thin. Collectibility grade: Fine.
Interesting Facts
Unlike most predatory snails, Turritella are ciliary feeders. They remain buried in the sand and filter organic particles from the water. Fossilized beds of similar species create ‘Turritella Agate’ or limestone used in construction.
Ecological Role
Sedimentary filter feeder. They play a vital role in processing organic matter in the benthos and serve as homes for small hermit crabs once the snail dies.
Similar Species
Turritella communis (smaller, found in Europe) and various Terebra species (Auger shells), which can be distinguished by their flatter whorls and predatory anatomy.
Beach Finding Tips
Look in the 'wrack line' after a storm or during low spring tides on sandy flats. They are often found partially buried or tangled in seaweed.