Opihi

Opihi, makaiauli or Cellana exarata. These limpits are a Hawaiian delicacy, kind of like the Hawaiian version of abalone. So much so in fact that they're pretty tough to find except on steep cliffs splashed with huge waves like this nice cliff here. At this point, they are nearly extinct on Oahu and in decline on the neighboring islands.

There are three endemic species of limpit (aka Opihi) in Hawaii. Their ancestors probably drifted over to the islands on driftwood. The less-favored black-footed 'opihi, makaiauli (or Cellana exarata), was the first to arrive and speciate into a unique Hawaiian species. The two other species could have derived from that original species or from other later introductions into Hawaiian waters. The other two species include the yellowfoot 'opihi or 'alinalina (Cellana sandwicensis) and the bigger kneecap 'opihi or ko'ele (Cellana talcosa).