Nick Upton / Common prawns (Palaemon serratus) scavenging on a damaged Flat top shell (Gibbula umbilicalis) in a rockpool, Cornwall, England, UK, September.

Nick Upton / Cushion star (Asterina gibbosa) moving in a rockpool near a Flat top shell (Gibbula umbilicalis) and a Common prawn (Palaemon serratus), Cornwall, England, UK, September.

Nick Upton / Cushion star (Asterina gibbosa) moving in a rockpool near some Flat top shells (Gibbula umbilicalis), Cornwall, England, UK, September.

Alex Hyde / Detail of Purple Topshell (Gibbula umbilicus) found washed up on a beach. Claigan, Isle of Skye, Inner Hebrides, Scotland, UK. April.

Sue Daly / Pennant's Topshell (Gibbula pennanti) and Purple Topshell (Gibbula umbilicalis) sea shells on beach, showing difference between species, sea shells on beach, Sark, British Channel Islands.

Sue Daly / Purple Topshell (Gibbula umbilicalis) sea shells on beach, Sark, British Channel Islands.

Sue Daly / Purple Topshell (Gibbula umbilicalis) sea shells on beach, Sark, British Channel Islands.

Nick Upton / Common brittle star (Ophiothrix fragilis) moving over floor of rockpool encrusted with red algae (Lithomnanion sp.) past Flat / Purple Top shell (Gibbula umbilicalis) low on a rocky shore, near Falmou...

Nick Upton / Broad-clawed porcelain crab (Porcellana platycheles) hiding behind Gutweed (Ulva / Enteromorpha intestinalis) in a rockpool alongide a Flat / Purple top shell (Gibbula umbilicalis) and a Limpet (Patel...

Nick Upton / Common brittle star (Ophiothrix fragilis) moving over floor of rockpool encrusted with red algae past Flat / Purple Top shell (Gibbula umbilicalis) low on a rocky shore, near Falmouth, Cornwall, UK, A...

Nick Upton / Common brittle star (Ophiothrix fragilis) moving over floor of rockpool encrusted with red algae past Common periwinkles (Littorina littorea) and Flat / Purple Top shell (Gibbula umbilicalis) low on a...

Nick Upton / Common brittle star (Ophiothrix fragilis) moving over floor of rockpool encrusted with red algae past Flat / Purple Top shell (Gibbula umbilicalis), Rough periwinkle (Littorina saxatilis) and Thick-li...

Sue Daly / Purple Topshell / Flat Top Shells (Gibbula umbilicalis). Channel Islands, UK, April.

Sue Daly / Purple Topshell / Flat Top Shells (Gibbula umbilicalis). Channel Islands, UK, April.

Stephen Dalton / Flat topshells (Gibbula umbilicalis) in rock pool, UK

Philippe Clement / Flat top shell (Gibbula umbilicalis) shell on beach, underside, Normandy, France

Philippe Clement / Collection of Trochidae with Pennant's top shell (Gibbula pennanti), Flat top shell (Gibbula umbilicalis) and Grey top shell (Gibbula cineraria), Normandy, France

Philippe Clement / Flat top shell (Gibbula umbilicalis) shell showing the aperture, Normandy, France

Philippe Clement / Flat top shell (Gibbula umbilicalis) shell on beach, Normandy, France

Philippe Clement / Collection of Trochidae with Pennant's top shell (Gibbula pennanti), Flat top shell (Gibbula umbilicalis) and Grey top shell (Gibbula cineraria), Normandy, France

Philippe Clement / Flat top shell (Gibbula umbilicalis) shell, Normandy, France

Simon Colmer / Beadlet anemone (Actinia equina) in rock pool with Common limpet (Patella vulgata), American slipper limpet (Crepidula fornicata), Flat top shell (Gibbula umbilicalis) and wrack seaweed, Sussex, UK

Simon Colmer / Green shore crab (Carcinus maenas) in rock pool with Beadlet anemone (Actinia equina), Common limpet (Patella vulgata), American slipper limpet (Crepidula fornicata), flat top shell (Gibbula umbilical...

Nick Upton / Two Common prawns (Palaemon serratus) foraging in a rockpool near a Flat top shell (Gibbula umbilicalis). Rhossili, The Gower Peninsula, UK, July.

Nick Upton / Common Hermit crab (Pagurus bernhardus) in a Dog whelk shell crawling over floor of a rockpool littered with shell fragments and grazing Flat top shells (Gibbula umbilicalis). Rhossili, The Gower Peni...

Duncan Usher / Flat Topshells (Gibbula umbilicalis), Common Northern Whelk (Buccinum undatum), and Common Periwinkle (Littorina littorea) shells