In the field, "bubbles" generally burrow in sand when the tide is low and begin moving about when it turns.
The broad flat head acts like a shovel to help burrow; the smooth shell and copious slime smooth the way under the sand. Eyes are not on stalks but on the top of the head.
These turned up in an area where I'd never seen them before on our 2004 trip.
A common rock-dwelling mollusk.
Two specimens: the left one is upside down and beginning to right itself. A beautiful animal
A lovely little Columbellid, the tip of these shells is usually gone - broken off by the animal for some reason.
An unusual and welcome find.
A very common Buccinid found in sandy and muuddy bays.
An unusual color for this species. Note the blue eyes.
A "worm shell" cements itself to a hard surface, but I was able to get this one off alive and intact.
Closeup of the aperture shows the animal within. It actually has a small operculum, not visible in the photograph.
A pretty, inch-long top shell.
Look closely and you'll see the foot is divided in half longitudinally - the animal slides first one side, then the other, to move.
There's no end to the color variations of these small (1/4-1/2") shells. The aperture is bright chestnut but the back can be any combination of black, white, blue, red, orange, yellow, etc. They live in large colonies in intertidal mud and small rocks.
These animals are nudibranchs and have no shell. In the field they are found under rocks balled into an amorphous blob.
There are well over a dozen ark shells attached to this rock. Any rock in a sandy bay is a miniature reef, with many shells, seastars, shrimps, crabs, etc. taking shelter in, on, and under it.
Can you spot these three shells in the photo? (Turbo to left of the rock in the sand; Pen shell in sand below the rock; Eupleura ("drill shell") on top of the rock, blending with it.
Found burrowing in the sand. When the tide turns, they pop out of the sand where they have been riding out the low tide and begin hunting for food.
Also burrow in the sand. The broad foot helps them shovel the shell down into the sand quickly.
Less than an inch in size, this is very common on the sand bars in the Baja.
Not as common as Florida coquinas, I feel lucky to find a live shell burrowing as the tide turns.
Terebras eat the worms that make small hills in the sand. During low tide they shelter under the sand.
Covered with mud by the receding tide, this shell is hard to spot nestled up against a rock.
Turned over. When cleaned, this will be a lovely light orange with a bright orange-red aperture.
These murexes get together to spawn and create masses of eggs as large as a yard across. The light-weight egg mass blows up on shore after hatching and looks like a plastic float.
The animals are so intent on laying their eggs that they lay them on each other, trapping some of the mothers inside the egg case. Later, after hatching, you can find egg masses with shells still inside them. One mass had about 250 shells in it!
This cowry lives under rocks in the intertidal zone. With its mantle up, it is difficult to distinguish from the plant and animal life encrusting the rock.
A beautiful animal with pink protrusions on the mantle.
Another prize is this beautiful red-spotted shell.
Eating mat anemones (sea anemones that live so close together they form a mat), these animals burrow between the anemones during low tide and emerge when the tide returns.
I once found about 75 of these animals in a yard-square mat of sea anemones. They are about 3/4 inch in maximum size.
Many Mexicans living near the sea eat molluscs. They discard the shells near the beach, where we are happy to pick them up!
Sometimes we are fortunate to find a diver who brings up shells to sell. This man scuba dives in a non-protected area and we purchase Spondylus, Nodipecten, and several Murex species, among other shells, from him.