from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. Any member of the Cardiidae.
from The Century Dictionary and Cyclopedia
- n. A bivalve mollusk of the family Cardiidæ.
Sorry, no etymologies found.
This one seems to be one of the common cardiid shells Cardiidae.
It features a carbonate beach, and the water has a high level of salinity--hence, the abundance of cardiid cockles, a species of bivalve that thrives in high salt concentrations, on Shell Beach.