sagitta

(plural sagittae))

the otolith in the sacculus, the largest of the otoliths except in Cyprinidae and Siluridae. Also called sacculith. It has been used for identification of species, for identification from remains in the diet of other organisms, and from remains in archaeological sites. The anterior end is pointed and the posterior end is rounded, straight or may be notched. Mesially it has a groove, the sulcus acusticus, which divides the otolith into dorsal and ventral halves and is margined by superior and inferior crests. The posterior branch of the acoustic nerve runs along the sulcus. The expanded anterior opening of the sulcus is called the ostium and has pointed margins, the longest being called the rostrum and the shorter the antirostrum. The posterior end is called the cauda (and may not extend to the otolith margin). The cauda may have dorsal and ventral points, the pararostrum and postrostrum respectively. A narrowing of the sulcus is called the collum and is the focus of sagitta formation. The upper rim is shorter than the lower rim and rims may be scalloped or have bulging domes