Three families inhabiting Korean waters A Ferosagitta robusta (Sagittidae) B Pterosagitta draco; C Krohnitta subtilis (Krohnittidae). Abbreviations: AF = anterior fin; CC = corona ciliata; COL = collarette; CF = caudal fin; E = eye; GS = grasping spine; LF = lateral fin; PF = posterior fin; SV = seminal vesicle; VG = ventral ganglion.