Ammo Knights

The Ammo Knights (アンモナイツ) are fishmen who serve as the Royal Guards for the Neptune family on Fishman Island. They wear large striped snail shells as helmets and shoulder pads with their eyes covered by a black mask of some kind. The helmets have a spike sticking out in the front, similar to a that of a unicorn. They carry tridents with them.

Trivia

 * Ammo Knight is a play on the word ammonite, the fossilized remains of the shells from snails or snail-like organisms, given that the knights wear such shells as part of their uniforms.