shells is a form of:

Perpetuation



noun
1.
(បច្ចេកទេស) ការធ្វើអោយនៅមានជាប់រហូត, និរន្តកម្ម
ENGLISH MEANING
noun
1.
The act of making perpetual, or of preserving from extinction through an endless existence, or for an indefinite period of time; continuance.