I found this Xiphactinus skull plate last weekend. It may not look like much, but it is one of my best finds so far. (I still need to do some prep work)
Those are small shelled creatures from long ago. They call them "rice crispies" Haha!
This came from the same (or close to the same) material you are getting your ecchinoids, and usual suspects from. I'm guessing that we hunt the same area in general, so if you ever want to go out, let me know.