Found this bone over a week ago. When I pulled it up out of the river I wasn't sure it was even a bone. I did think it had enough interesting features to take it home and investigate further. After soaking and softening up sand and pebbles lodged in small openings I was able to clean it up a bit. At that point I started to see characteristics that made it look like another ear bone. A search of the web turned up what looks like a good comparison from the Charleston Museum website. They have a photo of an "undescribed mysticete cetacean" whale ear bone, an auditory bulla (object ID: PV243