unknown sedimentary rock

This rock is comprised of medium and smaller crystals 0.08 inches (2 mm) or smaller. The crystals creating this rock are predominantly a dull grey color. The most notable feature of the rock is the presence of several well-preserved fossil crinoids (prehistoric animals whose relatives still exist today and are called feather stars) on the top face. Because these are exclusively marine animals it indicates this rock formed in the ocean. The rock doesn’t scratch easily and is fairly hard. Despite its certainty of forming in the ocean this rock doesn't have a salty taste. A drop of acid on the rock surface results in rapid and immediate effervescence (fizzing and bubbling) suggesting the crystals making it are likely calcite or a similar carbonate mineral. Lapworth Museum of Geology CC BYNC(4.0) via sketchfab [https://creativecommons.org/licenses/by-nc/4.0/legalcode]