A sand collar is the egg case made by moon snails, of the
family Naticidae. The eggs are laid in a gelatin-like matrix with which
sand grains are mixed. The individual egg capsules can be seen under a
magnifying glass or microscope. When the little snails hatch, they swim
around for a while before settling on the bottom.
Clams and oysters in the shell should be alive and the shells
should be closed tightly or should close when the mollusks are tapped.
The U.S. Public Health Service, in cooperation with the States, has a
sanitation control program that covers the labeling and shipment of
clams, mussels, and oysters. These shellfish may be harvested only from
non-polluted waters and processed for shipment in sanitary plants
inspected by State shellfish inspectors. Authorities periodically test
water for sewage pollution and ban catches from polluted areas.