This is the Large Necklace Shell (Euspira catena), a distinctive marine snail found around the British Isles, extending to the North Sea and the Mediterranean. This particular specimen was recorded as having been collected in the Bay of Biscay.

Location:
Northeastern Atlantic, including the British Isles, North Sea, and Mediterranean. Found on sandy or muddy seabeds from the low water mark down to depths of around 125 metres.

Average Size:
Typically grows to around 3 cm in diameter.

Family:
Naticidae (Moon Snails)

Species:
Euspira catena

Shell Characteristics:
The shell is smooth, glossy, and typically buff or pale yellow in colour, with a delicate row of brown markings spiralling around the last whorl—giving it the appearance of a necklace.

Feeding:
A predatory species, the Large Necklace Shell feeds primarily on bivalves. It uses its radula and acidic secretions to drill neat holes into the shells of its prey to access the soft body inside.

Reproduction:
This species is known for its distinctive egg-laying behaviour. The eggs are embedded in a collar-shaped, jelly-like mass that becomes coated with sand, often found on sandy seabeds.

Ecological Role:
As an active predator of bivalves, the Large Necklace Shell helps regulate populations of small molluscs within its habitat, contributing to the balance of benthic ecosystems.