The Collaborative International Dictionary of English v.0.48:

Nullipore \Nul"li*pore\, n. [L. nullus none + porus pope.]
   (Bot.)
   A name for certain crustaceous marine algae which secrete
   carbonate of lime on their surface, and were formerly thought
   to be of animal nature. They are now considered corallines of
   the genera Melobesia and Lithothamnion.
   [1913 Webster]