The « Giant Tugali Limpet » is a very large fissurellid native to northwest Pacific, with a distribution ranging from northern Korea and Japan (north of Fukushima Prefecture) to Sakhalin. A rather uncommon algae-grazing herbivorous species, it inhabits hard rocky substrates of intertidal to shallow subtidal waters down to about -30m deep. Although the shell is not colourful, its soft parts are vivid and brightly coloured in orange to red and the foot is larger than the shell. A shallow notch in the anterior end of the shell proves that it is a slit limpet, but this feature is often very inconspicuous in gerontic specimens. Typical shell length around 70mm., very large specimens may exceed 95mm. It used to be placed in the genus Tugali (hence the comm.on name), but is now moved to Scelidotoma. Although the external appearance is similar to abalones, its flesh is said to taste bitter and vile when raw and tasteless when cooked. It is one of the host species of the symbiotic scale worm (Polychaeta: Polynoidae) Arctonoe vittata (Grube, 1855), which lives in the pallial groove of the host. The host helps the worm move about and protects it from predators, the worm does not feed on the host and in return helps the host fight predators such as sea stars by biting them.

Finding location: Coast of Yagi, Hirono-cho, Iwate Prefecture, Japan.