The Collaborative International Dictionary of English v.0.48:

Gyrogonite \Gy*rog"o*nite\ (j[i^]*r[o^]g"[-o]*n[imac]t), n. [Gr.
   gy^ros circle, ring + go`nos fruit.] (Paleon.)
   The petrified fruit of the Chara hispida, a species of
   stonewort. See Stonewort. --Lyell.
   [1913 Webster]