Here is an Ordovician horn coral found in eastern Jefferson County, Kentucky. I sliced off the top part that was covered with debris using a diamond saw. You can see the borings of probably a worm. The image shows the top few that has been polished with wet sand paper and the side view showing multiple boring marks.
See this neat website on bioerosion (http://www.wooster.edu/geology/Bioerosion/Trypanites.html) by a worm like creature called Trypanites. Boring marks are seen quite a bit on horn corals but I rarely find them going through to the septa. This one did but I should have preserved the distal end to see if it was more a rounded or flared.