“…Chlamydinae with plesiomorphic sculpture of antimarginal ridgelets present from edge of prodissoconch on LV and from edge of proximal calcitic area on RV, but variously modified by intersection with commarginal ridges in many taxa; with small posterior auricles with a weakly concave posterior outline, at least in early lineages; most taxa retaining much larger anterior auricles than posterior ones into adulthood, retaining a deep byssal notch in the RV, although some relatively large taxa, for example Equichlamys bifrons (Lamarck, ), Zygochlamys delicatula (Hutton, b ) become free‐lying when adult, lose the ctenolium and develop a shallow byssal notch; with complexly subdivided and intercalated radial costae, increasing in number as shell grows; lacking prominent, narrow carinae on interior expressions of radial costae (internal rib carinae), except in a few species, for example Equichlamys bifrons , Notochlamys hexactes (Lamarck, ); with simple and, in most taxa, low, narrow resilial and dorsal hinge teeth; and with shagreen microsculpture, at least in early lineages and on proximal area of disc of many Cenozoic and living taxa.…”