Snails are a marine mollusk. They begin with the letter S.
Ormer, found off the Scilly and Channel Isles.
mussel
Abalone is an edible marine mollusk that begins with the letter A. It is a type of sea snail commonly found along coastal waters.
Aplacophora
mussell
The country name that beginning with 'A' but not ending in 'A' is Azerbaijan
Oyster Michele
crustations
Mollusc is the scientific name. There are many different molluscs, each with a different scientific name.[In the US, the spelling mollusk is used.]
Pippin.
There hasn't been one with three letters beginning in u and ending in n.
assegai