I described Lyrodiscus Rogers, 1967 as a new genus (Rogers, 1967). This name is an invalid junior homonym of Lyrodiscus Pilsbry, 1893. Williamsius is proposed as a nomen novum to replace Lyrodiscus Rogers, 1967. The name is in honor of Lucy Bunkley-Williams and Ernest H. Williams Jr. and their work with fish parasites.
I thank Joseph R. Sullivan, Piedmont, Oklahoma, for advice in forming the Latin name.