  A semiempirical shell model mass equation based on magic number Z=126 and
applicable to translead elements with N smaller or equal to 126 is presented.
For alpha decay energies the equation is shown to have a high predictive power
and an rms deviation from the data of about 100 keV. The rms deviations for
masses and other mass differences are between about 200 and 300 keV.
