1982  Nishida & Kyuma, p.3: The coralgal biolithite is
           distributed in the northeastern part and comprises the
           alternated layers of algal stromatolites and chaetetid
           of some decicentimeters in thickness and rather thinh
           skeletal debris mainly composed of crinoid stem
           ossicles.
           Pseudostafella antiqua Zone of Akiyoshi Limestone
           Group.
     1998  Nishida et al., 1998, p.5, text-fig.3: uppermost part
           of antiqua Zone.