Please pop into the AMC to let us have a closer look at it. I cannot tell from the photographs. We are open Monday to Friday from 10.00 am to 5.00 pm. It might be worth telephoning or emailing the Identification & Advisory Service first so that we can find the right specialist to help you on the day.
Hope to see you soon,
It's a Calamites fossil from the Carboniferous period. I find loads of them in West Yorkshire. Calamites are in the group horsetail plant because the lines going down them look like a horses tail.
Missed this post and came to London last weekend with my Echinoids from the IOW, unfortunately the AMC was closed but this did not matter because there was a lot more to do in the NHM.