Short answers, pulled from the story.
Clams are bivalve molluscs, meaning they have two calcareous shells joined at a hinge by a flexible ligament. They are filter feeders that spend most of their lives buried in sand or mud on the sea floor or in riverbeds, living in both freshwater and marine environments.
Clam lifespans vary enormously by species. Some species complete their entire life cycle in a single year, while the ocean quahog, Arctica islandica, has been confirmed to reach an age of more than 500 years.
Clams are eaten by both the Pacific and Atlantic species of walrus, all known subspecies of harbour seals, most species of sea lions including the California sea lion, bearded seals, river otters in Asia and North America, and numerous bird species including the Eurasian oystercatcher, whooping crane, and American flamingo. Most species of octopus, including the Giant Pacific octopus, also rely on clams as a staple food.
Wampum is a form of sacred jewellery and shell money historically manufactured by the Algonquians of Eastern North America. It was made from Mercenaria mercenaria, the hard clam, which is also the species most commonly eaten along the eastern United States and the Maritimes of Canada today.
In Islam, clams are considered halal in three Sunni madhhabs but are not permitted in the Hanafi school, which restricts aquatic animals to fish only. In Judaism, clams are not kosher.
On the eastern coast of the United States and Maritime Canada, the hard clam, Mercenaria mercenaria, is the dominant culinary species. Other commercially important Atlantic species include the soft-shell clam, Mya arenaria, the ocean quahog, Arctica islandica, and the surf clam, Spisula solidissima. On the West Coast, the butter clam, Pacific razor clam, gaper clam, geoduck, and Pismo clam are all eaten as delicacies.