Fig. 8From: Ontogeny and morphology of the retrochoanitic septal necks of Agoniatites vanuxemi from the Middle Devonian Cherry Valley LimestoneDiagrammatic cross-sectional representation of the septal necks of Agoniatites vanuxemi. S siphuncular tube, VSN ventral septal neck, DSN dorsal septal neck, aux auxiliary deposits, VW ventral shell wall, arrow indicates the adoral directionBack to article page