astrorhiza

from The Century Dictionary.

• noun [lowercase; pl. astrorhizæ.] In the fossil hydrocorallines named Stromatoporoidea, one of the shallow stellate furrows on the surfaces of successive laminæ which radiate outward from numerous centers.
• noun A genus of foraminiferous rhizopods, typical of the family Astrorhizidæ and the subfamily Astrorhizinæ. The species are of considerable size.