A cut block of Portland Stone with a fossil protruding out from the surface. The original shell material has leached away leaving only the external cast and the internal mould. The mould resembles a horse head with ears and a snout. Portland Stone is a white, fine grained, oolitic limestone.

The quarry men on the Isle of Portland call the casts and moulds of the fossil bivalve Trigonia ‘osses ‘eads (horses’ heads). This is why
#portlandstone #whitbed