Plagiostoma giganteum (J.Sowerby)

Lower Jurassic, Lias Group, Waterloo Mudstone Formation

Garron Point, Co. Antrim

K8445

largest 75 mm across

This is probably the most common large bivalve in the Lias Group of Northern Ireland. Occasional examples may be more than twice this size. Its smooth black or dark brown shell is particularly distinctive, differing from the rougher shell of the related Antiquilima, and can be identified from even small fragments.