Family XYSTONELLIDAE Kofoid & Campbell, 1929

Syn.	Xistonellidae

Lorica elongate, chalice-shaped; aboral end long and narrow; wall reticulate; all species marine (mainly eupelagic); a few fossil forms known.

Parafavella Kofoid & Campbell, 1929. Many to very many species.
Parundella Jörgensen, 1924. Many species.
Xystonella Brandt, 1906 (syn. Xistonella). Several species.
Xystonellopsis Jörgensen, 1924. Very many species.
Incertae sedis:
Parafavelloides Deflandre & Deflandre-Rigaud, 1949. Single or a few (fossil) species (but never properly described?).