Although the burrows and trails in the Upper Ordovician rocks around Cincinnati, Ohio, have been fully documented and are well known (Osgood, 1970), comparatively little attention has been paid to the borers. Nevertheless, borers are very common in a variety of hard substrates in these rocks. These substrates include the skeletons of bryozoans, corals, and stromatoporoids (Palmer and Wilson, 1988), as well as cobbles and hardgrounds (Palmer, 1982; Wilson, 1985). By far the most common type of boring is the elongate tube Trypanites, which could have been made by a variety of filter-feeding worms. Trypanites is common on hard substrates throughout the lower Paleozoic (Palmer, 1982).