This is one kind of volute. I saw some information about it via Wikia Media
Melo Melo, common name the Indian volute or bailer shell, is a very large sea snail, a marine gastropod mollusk in the family Volutidae, the volutes.
This large sea snail is known to live in littoral and shallow sublittoral zones. It usually dwells in muddy bottoms at a maximum depth of nearly 20 m.[2]
Its scientific name is Melo Melo. In Vietnam, it's quite rare and it's often found mainly in the Sea of Central Vietnam. In Vietnam, It's called as a variety of names. Somewhere people call it as "ốc gàu, ốc gáo" (meaning "scoop" because its shell is large enough to be used as a scoop). Somewhere people call it following its shell color such as ốc vàng (yellow volute), ốc giác...
Its maximum weight could be up to 5 kgs, but often during the amount of from 0.5-3kgs per one. Its shell is quite large and hard. The outside of shell color is commonly pale orange, sometimes presenting irregular banding of brown spots, while the interior is glossy cream, becoming light yellow near its margin. People have an interest in its shell. Its shell is used as a decoration item, even as a water container, as a scoop.
Usage:
This kind of volute is often used to export. Especially, those are mainly used in the high-quality restaurant because of the high nutrition and nice taste.
Each Melo Melo can produce lots of meat. A 1,5 kg Melo Melo could give you about 1,3kg meat. You can use all of its meat without leaving anything except for its shell.
I would like to share my experience to use it. Firstly, boils it in water until the water boils at 100*C about 20 minutes. Then, pull it out to peel the shell. The last step, boil it again in hot water about 15 - 20 minutes.
After that, slice it into small pieces and use directly with chili sauce. Or use with mango slices as a salad. Very delicious. I can say for sure ;)
Nowadays, fishermen still hunt it for pearls. But its pearls are extremely unique. Maybe among a million volute, there is a small pearl. Its pearl is not similar to the ordinary pearl. This is quite large and is light yellow. The older it is, the more beautiful the pearl is.
Each pearl costs about 200 millions - 450 millions VND.
(Two last pics from Internet)