Myophorella incurva Benett.
Internal cast of an articulated Bivalve in cherty matrix. These rather strange looking fossils were known in folklore as 'Osses' Eds' due to their vague resemblance to the head of a horse from a certain angle. Very nice example.
Jurassic, Portland Stone.
Isle of Portland, Dorset.
Bivalve : 5 cm long.