| _Central capsule_ | _Central capsule_ | | originally ovoid, | always spheroidal, | | monaxon. | monaxon. | | | | | _Capsule-membrane_ | _Capsule-membrane_ | | single, | always double, | | a porous area | an astropyle | | (porochora) at the oral | (with radiate operculum) | | pole of the main axis. | at the oral pole | | | of the main axis. | | | | | _Nucleus_ excentric, | _Nucleus_ always spheroidal, | | near the aboral pole | in the main axis | | (dividing late). | (dividing late). | | | | | _Skeleton_ siliceous, | _Skeleton_ of a silicate, | | usually monaxon, | always extracapsular. | | extracapsular. | | | | | | _Calymma_ always | _Calymma_ always | | without phæodium. | with phæodium. | +-----------------------------------------------------------------+