The fossil the blue arrow is pointing to appears to be a Palaeoconchus (aka Spirobus) worm fossil. It was found in the Glen Dean formation.of Grayson County,
Kentucky USA. The fossil dates to the Mississippian Period. The worm fossils is intermixed with bryozoans (maybe Fenestella). Image was taken with a microscope with an approximate 4 mm field of view (FOV).