An impressive area of moist saltmarsh was covered with these molluscs. I estimate that they were 5mm at maximum.
No interactions present.
whereas Assiminea grayana is more rotund at 5mm by 3mm. What do you think?
Yes. by shape it does look more like Assiminea grayana. I'd forgotten this was a possibility on east coast saltmarshes and assumed it was the more widespread Hydrobia/Perinia ulvae. On size though, they're pretty similar. H. ulvae is more like 5mm x 3mm, max 6mm length according to this site:http://species-identification.org/species.php?species_group=mollusca&id=734
Nick Upton, naturalist and photographer.
Lat/Lng: 53.4249, 0.2062
OS grid ref: TF466942