Large mollusc in Monterey Bay help

[Todd128]

I spotted a large snail-like mollusc today diving Monterey Bay and would like some help with an ID please. Most of the critter was it's large oval foot--which was transluscent grey-blue in color. The foot extended well outside of it's relatively tiny, pearlescent white spiral shell. The shell had some highlights of grey-blue, and was maybe 1-2" in diameter. There is no way the foot or exposed body could fit into that tiny shell. Additional detailed info below. Many thanks for sharing your expertise. Todd

(1) How big is the critter?

About 1 foot long, about 6" wide...about the size of a Gumboot chiton

(2) Where in the world is the critter?

Pacific Grove, at Lover's Point (Monterey Bay, CA, USA)

(3) What sort of habitat (reef, wreck, sand, rubble etc) is the critter in?

Sand bottom

(4) How deep is the critter?

25-30 feet

(5) What time of day (or night) did you see the critter?

About noon

(6) Any observed behavior of the critter...

Trucking along the sand bottom at full speed

(7) If the locals have a common name for the critter, what is it?

 

[LeslieH]

That's a moon snail, genus Euspira. The name change is recent so you'll find most references to it under the old name Polinices. There are several species in the area; the one you saw might be E. lewisii which is common there & one of the bigger ones. They plow along sandy or muddy bottoms searching for clams. When they find one they bore a hole through the shell & eat the clam within it's shell.

The first link is a picture of a moon snail on Northwest Diver, an excellent resource for identifying critters & learning more about them. Metridium Fields is of animals around Monterey & Divebums for southern California & Baja.

http://www.northwestdiver.com/gallery/showphoto.php/photo/1519/cat/501/si/moon snail/perpage/12
http://www.metridium.com/
http://www.divebums.com/main.html