This is the right hand half of a shell of a brachiopod with a very long hingeline. Strong ribs are visible, but the shell is very flattened, being preserved in slate. In life it would have looked like the cyrospirifer preserved in calcite, DBR 5.0. From the Delabole slate quarry, Cornwall, where they are known as Delabole butterflies.
Size: 60 x 30mm on a block 80 x 55mm
Size: 60 x 30mm on a block 80 x 55mm