from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Of or pertaining to periostracum.
from The Century Dictionary and Cyclopedia
- Investing the shell of a mollusk, as an epidermis; of or pertaining to periostracum.
Sorry, no etymologies found.
Clear differences can be seen in the number of whorls and location of periostracal hairs in the embryos, though.