Radiolaria are marine protists that are most abundant in tropical waters. The remains of their beautiful houses can be found on the bottom of the ocean as well as in fossilised rock.

Direct link: http://www.microscopy-uk.org.uk/micropolitan/index.html

From the Institute for the Promotion of the Less than One Millimeter’s
Micropolitan Museum (the marine collection)

Link: http://www.microscopy-uk.org.uk/micropolitan/index.html