Tiny (c5mm) with pronounced ridges on shell
No interactions present.
The animal that was once called Littorina saxatilis is a complex of species including L neglecta, L nigrolineata and L.arcana, L.rudis,L.tenebrosa and L.saxatilis that can be quite hard to separate from each other. The status of the species isn't agreed on by the taxonomists; some are certainly valid but others (including L.saxatilis) may not be. Worse still, separation of some species needs close examination of the reproductive system. Sorry !
Oh well, worth a try. I think my knowledge is a bit out of date!
Lat/Lng: 50.0459, -5.1761
OS grid ref: SW727210