rhabdolith

from The Century Dictionary.

• noun A minute rhabdoidal concretion of calcareous matter occurring in globigerina-ooze—one of the elements which cover a rhabdosphere.

from the GNU version of the Collaborative International Dictionary of English.

• noun A minute calcareous rodlike structure found both at the surface and the bottom of the ocean; -- supposed by some to be a calcareous alga.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A minute calcareous rodlike structure found both at the surface and the bottom of the ocean, supposed by some to be a calcareous alga.