Giant Keyhole Limpet

Scientific name: Megathura crenulata

Common name: Giant Keyhole Limpet

Range: Central California to Baja California.

More information: Entry from Molluscs [sic] of Orange County; possibly worth learning more about: immunological studies of Giant Keyhole Limpets; hemocyanin

Believe it or not, a limpet is a primitive type of gastropod (snail), and that's what this is. He obviously doesn't fit within his shell, though. Now, this is the only Giant Keyhole Limpet I've yet encountered, but, from all the photos of other specimens I've seen, this guy is unique in having an extremely small shell given his body size. The others are big, but the shell doesn't seem nearly as useless on them.

According to my Audubon field guide, the Giant Keyhole Limpet "feeds on algae and colonial tunicates. Native Americans used the conveniently perforated shell on wampum belts."

UPDATE, 7/7/07: I observed my second Giant Keyhole Limpet at a tidepool in Laguna Beach early last month. Its coloration was different from the above, and I got to see its underside and really get a sense of its anatomy. I will post photographs in a follow-up entry.