Like many snails, whelks have an operculum - a hard plate which acts like a door when the snail is pulled inside its shell.  It fluoresces under blue light.

Kellet's whelks lay eggs in the late spring.  They look kind of like oyster crackers:

These are leafy hornmouth egg cases, also visible in the 5th photo above (a leafy hornmouth orgy) and 6th photo (a leafy hornmouth that moved too slowly during an orgy and got laid on).

The egg cases fluoresce under UV light:

(1: San Carlos Beach, Monterey)

The foot is huge relative to the shell.  These cruise along underneath the sand, often with just their eyes, snout, and shell visible:

Moon snails lay their eggs in a collar shape.  The third picture shows a snail laying eggs.

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Money Wentletrap

In the first picture, the snail on the right has extended its mantle all the way around its shell.  That's why olive snail shells are shiny, compared with shells where the snail stays on the bottom.  You can see the mantle retracting in the second photo.

These are often found in large numbers in the sand just past the surf zone:

(1-4: San Carlos Beach, Monterey)

These are pretty tiny.

(1: San Carlos Beach, Monterey)

Extremely small; this one is only 2 mm (1/10") long.

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Red Top Snail

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Scaled Wormsnail

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Slipper Snail

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Striped Barrel Shell

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Three-Colored Top Shell

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Wavy Turban Snail

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Western Lean Nassa