There is a two-layered primary wall in Lamarckina, Hoeglundina, and several other members of the Robertinidae and Epistominidae. It thus seems probable that all members of the Robertinacea are bilamellar. A continuation of the inner lining over the septal face resembles the rotaliid structure very closely. Stomatorbina is a calcitic, primarily granular monolamellid with thick, radial secondary accretion. It does not belong in the Robertinacea and may be related to Valvalabamina.