tentaculite

from The Century Dictionary.

• noun A fossil pteropod of the family Tentaculitidæ.

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

• noun (Paleon.) Any one of numerous species of small, conical fossil shells found in Paleozoic rocks. They are supposed to be pteropods.

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

• noun paleontology Any of numerous species of small, conical fossil shells found in Paleozoic rocks.