keckia

from The Century Dictionary.

• noun A genus of fossil algæ belonging, according to Schimper, to the group Caulerpiteæ, of uncertain affinities, consisting of a phyllome from a cylindrical, apparently solid, many times branching stem, the branches arising at an acute angle, simple or again branched, gradually thickened upward, and covered with large thick, scale-like rings or annular swellings which leave crescent-shaped scars when removed, indicating that they were hollow or sack-like.