My Tonna galea is from southern Croatia.
Video of crawling Tonna galea on the sand in an aquarium (there is no audio):
Another video of the same Tonna galea (no audio):
The frontal view of Tonna galea usually looks like this:
Proboscis is a prehensile tube and there is a mouth at the end of the proboscis. Therefore it is an important part of the body of the sea snail. Proboscis is well innervated (there are nerves inside the wall of proboscis) and there are glands next to the proboscis. I found no exact measurements of the proboscis of such big Tonna galea sea snails in the literature.
Simone L. R. L. de 1995: Anatomical study on Tonna galea (Linné, 1758) and Tonna maculosa (Dillwyn, 1817) (Mesogastropoda, Tonnoidea, Tonnidae) from Brazilian region. Malacologia 37(1): 23-32.