Archerd Shell Collection> Shell Classes > Mid-Section of Shell
(Left) The shell of the tun mollusc, Tonna perdix, shows a rather beautiful architecture when cross-sectioned vertically, near the midline. While this is a rather delicate shell, the structure is nevertheless typical of many gastropod shells.
Note the vertical column, or columella, formed by twisting of the shell as the snail grows. A particularly large aperture at the opening of the final whorl is characteristic of the tun family (Tonnidae).
(Modified picture, from Wilson & Gillett, 1971)
Archerd Shell Collection> Shell Classes >Mid-Section of Shell