Callochiton septemvalvis Orkney, Scotland. March 1978.
The apophyses on the intermediate valves of C. septemvalvis are short (anterior-posterior), wide and gently curved. They meet at the jugum (1) with no jugal sinus (gap) between them. It is the only British species with two slits (2) and slit rays, sometimes a small third one (3), in the articulamentum on either side of the imtermediate valves, ii to vii.

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