Back in August I posted a picture of a Pisidium, a tiny clam (family Sphaeriidae) that was about 2 mm long. And now here is something from the opposite end of the size spectrum: Tridacna gigas, the largest known extant mollusk species. The shells of this species can grow up to 1.5 meters in length.
The pen provides a scale.
This particular specimen sits in the elevator lobby on the 3rd floor of the Smithsonian’s Museum of Natural History. It is an area normally closed to the public, and because of that nobody gets to see it except the people who work there. I was there last Tuesday working in the mollusk library, which is also on the 3rd floor. While waiting for the elevator on my way down I snapped this picture for all to see.
More information on Tridacna gigas:
Animal Diversity Web