Anatoma Woodward, 1859: 204.
+ (objective) Schizotrochus Monterosato, 1877: 416. Type species: Scissurella crispata Fleming, 1828 (M).
+ Hainella Bandel, 1998: 36–37. Type species: Scissurella euglypta Pelseneer, 1903 (OD).
not Anatomus Montfort, 1810 (Annelida: Polychaeta: Serpulidae. See McLean, 1967; Herbert, 1986).
Type species. Scissurella crispata Fleming, 1828 (M).
Etymology. Derived from Anatomus Montfort “spelled properly” (Woodward, 1859: 204; OD). Woodward’s spelling correction related to the Adams & Adams (1853 –1858) assignment of Scissurella crispata to Montfort’s genus Anatomus. Woodward noted that Anatomus referred to a serpulid polychaete, and that Scissurella crispata should be distinguished from other members of Scissurella: “If it should still be considered desirable to have a subgeneric name for Scissurella crispata, I have no objection to the adoption of Anatoma, provided it be spelled properly, and not attributed to Montfort.”
Description. Shell large (to 6 mm), trochiform. Spire prominent. Slit deep, open. Slit and selenizone at periphery or slightly above; keels usually prominent, at right angle to shell axis. Umbilicus open, often very constricted, no carina. Protoconch smooth or with flocculent sculpture, varix absent or faint, not forming bridge to nucleus of embryonic shell. Operculum multispiral with central nucleus, corneous, thin. Radula n5R5n, fifth lateral little to strongly elongated, but not broadened.
Differential diagnosis. Thieleella has a protoconch with sculpture of honeycomb pattern, whereas the protoconch of Anatoma is either smooth or has flocculent ornamentation. It is virtually impossible to distinguish members of these two genera under the light microscope.