This image is identified as Pinna lanceolata (J. Sowerby) bivalve fossil. They were found in the Corallian Beds Lower Calcareous Grit Scarborough Yorks England. The fossil dates to the Mesozoic Era, Jurassic Period, Upper/Late Oxfordian stage.
Fossils were on display at the British Natural History Museum in London, England on August 2016.