Wikipedia
Architectonicidae
Architectonicidae, common name the staircase shells or sundials, are a family of sea snails, marine gastropod mollusks in the informal group "Lower Heterobranchia" (= Allogastropoda) of the clade Heterobranchia.
The extinct families † Amphitomariidae Bandel, 1994 and † Cassianaxidae Bandel, 1996 belong to the same superfamily.