However, there are mtDNA identified errors in Family 5 which show that the family actually descends from three separate founder mares - see The Massey Mare entry

A different haplotype to the main family trunk appears in branches 5-g and 5-h descending from Miss West; this error originates in the 1891 GSB which says Miss West is a descendant of The Massey Mare, whereas previous editions had Miss West's ancestry ending in an unspecified Basto mare (not Old Ebony specifically), which therefore appears to have been correct,

so Old Ebony, the 3rd dam of this Regulus Mare, is probably not the ancestress of branches of branches 5-g and 5-h

Dam of Miss West (by Matchem) through which branches 5-g and 5-h supposedly descend

Grandam of Stargazer (1786 King's Plate Lincoln, 1787 Doncaster Cup, 1788 King's Plate [mares] Newmarket; of Quiz (1801 St Leger); and 4th dam of Barefoot (1823 St Leger)