Wiktionary
boring clam
n. A clam, (taxlink Tridacna crocea species), capable of burrowing even through rock.
Wikipedia
Boring clam
The boring clam, crocus clam, crocea clam or saffron-coloured clam (Tridacna crocea) is a species of bivalve in the family Cardiidae. It is native to the Indo-Pacific region. It is occasionally found in the aquarium trade where it is often simply referred to as crocea.