Found this on Holkham beach in Norfolk, photos below. At first sight I thought it was a bean sprout which had been dropped by someone but it's completely rigid. It's about 15mm in diameter. The base is rough like bone or some kind of shell whilst the strange tip is glassy, like hard plastic. It's hollow with thin walls - if I shine light through the hole in the bottom, it illuminates a spot on the wall from the inside. It's vaguely symmetrical but not as much as I'd expect from a bone, unless it has been bashed and worn down a bit. Any ideas? Thanks
This is a dermal denticle, a tooth like projection from the skin of various types of cartilaginous fish. The thorn back ray is a typical example, incidently they are the rays which lay the black square mermaids purse.