A kind of clam · also called whole clams, in-shell clams, shell-on clams

2 views: its portrait, and how it looks in the comparison photos.
About
Whole clams in their shells pack loosely, leaving empty air spaces between their hard, curved valves.
In the shell, clams have an average bulk density of about 44 pounds per cubic foot (0.7 grams per milliliter). Because of their rounded, rigid shells, they leave open pockets of air when piled together in a container. This makes a basket of whole clams noticeably lighter by volume than shucked clam meat or pure water.
From Wikipedia
Clam is a common name for several species of bivalve mollusc. The word is often applied only to those that are deemed edible and live as infauna, spending most of their lives halfway buried in the sand of the sea floor or riverbeds.
Read more on Wikipedia →Text from Wikipedia’s “Clam” article, CC BY-SA 4.0.
1 on the site
One cup weighs
5.84 oz (166 g)
Quick answer
One US cup of clams in the shell weighs about 5.9 ounces (166 grams). This is roughly the same weight as a cup of diced apples.
Typical figures, the same ones every comparison on the site uses; real ones vary.
More like clams in the shell
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Next to anything: a person, a car, another clam.