What does "sagitta" mean?

Additional senses

1. 2.(Geom.) The distance from a point in a curve to the chord; also, the versed sine of an arc; -- so called from its resemblance to an arrow resting on the bow and string. [Obs.]
2. 3.(Anat.) The larger of the two otoliths, or ear bones, found in most fishes.
3. 4.(Zoöl.) A genus of transparent, free-swimming marine worms having lateral and caudal fins, and capable of swimming rapidly. It is the type of the class Chætognatha.