I would really appreciate some help discovering what this discovery is. I found one in a limestone chunk a few years ago and never saw one until I found a spot that's filled with these things. They have some really nice calcite and a couple exceptional quartz crystals inside some of them and they break away easily from the matrix which appears to be in most cases part of the animal like in outer shell but the encasement or shell is usually pretty thick and there's usually more on one side than the other. Another unusual characteristic is they usually have parallel ridges formed that run lengthwise and some have spiky bumps on those ridges. Also found with nice horn corals. Jefferson County KY.