Retusa obtusa

Retusa obtusa, common name the "Arctic barrel-bubble", is a species of very small head-shield sea snail or bubble shell, a marine gastropod mollusk in the family Retusidae.

This species occurs widely in the northern parts of the Atlantic Ocean, occurring in both the Eastern Atlantic and Western Atlantic. It has also been reported from North Carolina, and from Alaska in the Pacific Ocean. The shell reaches a maximum size of 3 mm.