With sand collar (egg mass). Aka: Euspira lewisii, Lunatia lewisii, Natica lewisii, Polinices lewisii. IMAG2486
Found at the south end rocky spit of Constellation Marine Park 4/27/13
Previously known as Cypraea spadicea
I think. Doesn't look like either of the 2 periwinkle species in my book, but does look like one of the N. ostrina variations.
Dark purple with no encrustations. Lots of little clumps up in the high intertidal zone with the ribbed limpets.
San Diego County, California, US