A recent trip to an exposure of the Mahantango Formation near Seven Stars, PA yielded this giant Ancyrocrinus spinosus anchor. It's still embedded in the rock but you can see four spikes emerge from the bulb like base.
This is by far the largest specimen of this genera that I have ever found and only the second that I've found in the Mahantango Formation. The total length of the exposed bulb and spikes is about 4cm.
I posted a few years ago about some small anchors I found in a different part of the Mahantango Formation in Montour County, PA Here and a specimen that I found in the Windom Shale along Lake Erie in NY Here.