Rudimentary vestigial shell, young specimen.

Aperture occupies virtually whole of ventral/interior face (left hand image).
1: recurved pointed umbo (rostrum) overhanging concave interior.
2: trace of yellow viscera adhering to interior.
3: outer shell-layer (periostracum) extends to form broad flexible border beyond inner shell-layer.
4: limp, imperceptibly calcified, inner shell-layer on young specimen.
5: growth line on amber outer shell-layer (periostracum).
6: embayment on right side of shell.
7: indistinct radiating lines.

Height (longest dimension) 7.5mm, about 30% length of animal. Flamborough, England. September 2014. Leg. S.Taylor.