Fish Bones – Otoliths, Pharyngeal Arch These are remains from a fish called the freshwater drum (sheepshead). These were found in a refuse pit at an Oneota site in Onalaska. At the left is a pharyngeal arch—part of two matched pairs of plates in the fish’s throat, used for crushing mussels. The other four are otoliths, or “ear stones.” An otolith in each ear helps the fish with balance and movement. Two of the otoliths are burned. The three otoliths in the center are all lefts, and the one at the right is a right, from a smaller fish. These right and left otoliths came from four different fish, and the pharyngeal arch represents another, smaller fish, bringing the total to five. Different sides and sizes of fish bones help us figure out how many fish are represented—the Minimum Number of Individuals, or MNI.