Allerya Mörch, 1877 accepted as Williamia Monterosato, 1884 (source of synonymy)
Aporemodon G. C. Robson, 1913 (status source)
Brondelia Bourguignat, 1862 accepted as Williamia Monterosato, 1884 (source of synonymy)
Parascutum Cossmann, 1890 accepted as Williamia Monterosato, 1884 (source of synonymy)
Roya Iredale, 1912 accepted as Williamia Monterosato, 1884 (source of synonymy)
Scutulum Monterosato, 1877 accepted as Williamia Monterosato, 1884 (source of synonymy)
Williamia Monterosato, 1884 (basis of record)
Williamia japonica Habe, 1962 accepted as Williamia radiata (Pease, 1861) (source of synonymy)
Williamia kermadecensis (Iredale, 1912) accepted as Williamia radiata (Pease, 1861) (source of synonymy)
Williamia maxwelli B. A. Marshall, 1981 † (original description)
Williamia radiata Kuroda & Habe, 1961 accepted as Williamia radiata (Pease, 1861) (source of synonymy)
Williamia radiata nutata (Hedley, 1908) accepted as Williamia radiata (Pease, 1861) (basis of record)
Williamia radiata radiata (Pease, 1860) accepted as Williamia radiata (Pease, 1861) (basis of record)
Williamia rugulosa (Koenen, 1892) † (status source)