DIAGNOSIS (modified from Carlgren, 1949; modification in bold): Hormathiidae with welldeveloped pedal disc often attached to shells. Column divisible into scapus and scapulus; scapus with tubercles sometimes on longitudinal rows, more rarely in coronal tubercles on distal scapus. Scapus usually with more or less strong cuticle. Marginal sphincter musculature mesogleal, strong. Tentacles not more than 96, exceptionally few more, without mesogleal basal aboral thickenings. Same number of mesenteries proximally and distally. Longitudinal muscles of tentacles and radial muscles of oral disc ectodermal; latter sometimes mesoectodermal. Two well-developed siphonoglyphs. Six pairs of perfect and sterile mesenteries. Retractors diffuse. Cnidom: spirocysts, basitrichs, p -mastigophores B1 .
TYPE SPECIES: Hormathia margaritacea Gosse, 1859.
VALID SPECIES: Hormathia alba (Andres, 1881); H. andersoni Haddon, 1888; H. armata Rodríguez and López-González, 2001; H. castanea (McMurrich, 1904); H. coronata (Gosse, 1858); H. digitata (Müller, 1776); H. georgiana Carlgren, 1927, H. incubans (Gravier, 1918); H. indutus (Gravier, 1918); H. insignis (Stephenson, 1918a); H. josefi Zhiubikas, 1977; H. lacunifera (Stephenson, 1918a); H. marioni (Haddon, 1889); H. nodosa (Fabricius, 1780); H. pacifica Sanamyan et al., 2015; H. pectinata (Hertwig, 1882); H. spinosa (Hertwig, 1882) (Fautin, 2016).