This is the Dog Whelk (Nucella lapillus), a small to medium-sized marine snail in the family Muricidae. It is a predatory species commonly found on rocky shores and intertidal zones.

Location:
Widespread around the coasts of north-east Atlantic Europe, including the British Isles, from the Arctic south to Portugal, as well as islands such as Iceland and the Faroes. It inhabits rocky shores from wave-exposed cliffs to more sheltered areas.

Average Size:
Shell height usually ranges from 20–40 mm, with some individuals occasionally reaching up to 60 mm.

Family:
Muricidae (Rock Snails / Murex Snails)

Species:
Nucella lapillus

Shell Description:
The shell is broadly conical, with a short spire and a large final whorl. Typically, it has six or more whorls with spiral ridges separated by narrow grooves, crossed by fine growth lines. Shell colour varies, including white, grey, brown, yellow or banded patterns. The base has a short siphonal canal, and the outer lip of the aperture thickens and develops internal teeth as the snail matures.

Habitat:
Dog Whelks are commonly found on rocky shores from the mid- to lower shore, often among barnacles, mussels, and algae. They are capable of living on both exposed and sheltered rocky shores but are rarely found on soft sediment.

Feeding:
This species is a carnivore and predator. It preys on mussels, barnacles, and other small invertebrates. The Dog Whelk uses a radula and chemical secretions to bore holes through the shells of its prey, then releases digestive enzymes to liquefy the soft tissues, which it then ingests.

Movement and Behaviour:
The Dog Whelk is slow-moving and often hides in crevices or under rocks to avoid drying out during low tide and to escape predators. After feeding, it may remain stationary in a sheltered spot for several days before hunting again. It does not form dense beds but may occur in proximity to other individuals in food-rich areas.

Reproduction:
Male and female Dog Whelks are separate. Eggs are laid in small, vase-shaped capsules attached to rocks or crevices. Each capsule contains hundreds to a thousand eggs. Juveniles hatch as miniature crawl-away snails, bypassing a long pelagic larval stage. Snails typically reach maturity after a few years, and lifespan is usually 5–10 years, depending on environmental conditions.

Ecological Role:
As a predator, the Dog Whelk helps control populations of mussels, barnacles, and other invertebrates, influencing the structure of rocky shore communities. Empty shells and egg capsules also provide microhabitats for small marine organisms.

Conservation Status:
Dog Whelks are common and widespread on suitable rocky coasts. Populations may be affected locally by habitat disturbance, pollution, and changes in community structure, but the species is not considered globally threatened.