gyrogonite

Century Dictionary and Cyclopedia

1. n. A petrified spiral seed-vessel of plants of the genus Chara, found in fresh-water deposits, and formerly supposed to be a shell.

Wiktionary

1. n. paleontology The petrified fruit of Chara hispida, a species of stonewort.

GNU Webster's 1913

1. n. (Paleon.) The petrified fruit of the Chara hispida, a species of stonewort. See stonewort.