Here's a whole wall of Nucella lamellosa eggs on a boulder at low tide.
These Nucella lamellosa (Wrinkled Dogwinkles) are laying egg cases!
Certain rocks have masses of Nucella lamellosa (Wrinkled Dogwinkles) laying their eggs on the same side, often facing the surf. The egg sacs look like honeycomb, and are called sea oats.
All are white.
Is this instead a dog whelk - Nucella lapillus?
During the week of March 30th, large numbers of these suddenly came to the high tide zone and congregated on large boulders. I assume laying eggs?