from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Relating to the cerebral cortex.
- adj. Relating to the mantle of a mollusk, brachiopod, or bird.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Of, pertaining to, or produced by a mantle, especially to the mantle of mollusks.
- adj. Of, or relating to, the pallium
from the GNU version of the Collaborative International Dictionary of English
- adj. Of or pertaining to a mantle, especially to the mantle of mollusks; produced by the mantle. See Illust. of bivalve.
from The Century Dictionary and Cyclopedia
- Of or pertaining to a mantle or pallium.
- Specifically, in conchology, pertaining to the pallium or mantle of a mollusk.
- Relating to the pallium or cerebral cortex.
Compare the photo with this drawing of the pallial cavity of Arion distinctus (from G.M. Barker, Naturalised terrestrial Stylommatophora [of New Zealand], 1999).
Compare the photo with this drawing of the pallial cavity of Arion distinctus from G.
According to Houbrick, the pallial eye may help detect predators.
A day later, I was even more fascinated when I spotted the pallial eye of a live C. scalariformis for the 1st time.
The pallial eye of Cerithidea scalariformis arrow.
Perhaps, the tentacular eyes are not suitable for terrestrial vision and the pallial eye evolved to take over their function on land.
The 2 usual eyes are at the tips of the snail's tentacles, while the 3rd unpaired eye, the pallial eye, is at the edge of mantle situated near the corner of the aperture.
To see a crawling snail's pallial eye, you need to look at the snail from slightly below.
The pallial eye is easy to notice when the snail lifts its operculum up and starts to come out of its shell with the aperture facing up.
Drawing of retracted Cerithidea scalariformis showing the operculum and the pallial eye pse.