The Lined Top Shell (Phorcus lineatus), commonly called the lined or toothed top shell, is a small marine snail in the family Trochidae. Its solid, globose-conic shell ranges from 10 mm to 35 mm in height and breadth, with six to seven convex whorls and a short spire. The shell is typically dull greyish or greenish, densely covered in fine, wavy or zigzag purplish-black lines, often showing an eroded orange apex in older individuals.

Location:
Rocky shores of the eastern North Atlantic Ocean, from Morocco and Portugal northward to Ireland and Wales. Found mainly in the mid- to lower-intertidal zone under boulders, among cobbles, seaweed, and in rock pools.

Average Size:
Between 10 mm and 35 mm in height and breadth.

Family:
Trochidae

Species:
Phorcus lineatus

Ecological Role:
A grazing herbivore that uses its radula to scrape microalgae, diatoms, and biofilm from rock surfaces, helping to control algal growth on rocky shores.

Conservation Status:
The lined top shell is not commercially fished but sometimes collected by enthusiasts. They serves as a bioindicator for coastal metal contamination. Scientists collect and analyse these snails to measure metal concentrations in their tissues or shells. By comparing levels across different locations or time periods, researchers can assess the extent and impact of metal pollution in coastal ecosystems.

Localised over-collecting and habitat disturbance can impact populations, so sustainable harvesting is encouraged.

Collection Date:
This specimen was collected in Plymouth in 1899.