Ventral & dorsal views of intermediate valve v from 8.6 mm long specimen.
1: Tegmentum; dorsal layer of aragonite permeated and weakened by canals
2: Articulamentum: ventral layer of aragonite; has triangular apophyses (3) projecting beyond tegmentum to underlie next valve.
Valve has gently curving, almost parallel, anterior (4) and posterior (5) edges, with somewhat obliquely truncated anterior corners (6), and lacks any sign of a beak (7).
Llŷn, North Wales. March 2016.