Pectinidae, Propeamussiidae and Entolliidae belong to the class of bivalved molluscs.
Class: Bivalvia Linnaeus, 1758
Subclass: Pteriomorphia Beurlen, 1944
Superorder: Eupteriomorphia Boss, 1982
Order: Ostreoida Waller, 1978
Suborder: Pectinina Waller, 1978
Superfamily: Pectinoidea Wilkes, 1810
Family: Pectinidae - Propeamussiidae - Entoliidae
Although more than 1000 recent species names can be found in litterature, most of those names degrade into the many synonyms and forms. There are about 500 different recent species accepted.
Shells belonging to the family Pectinidae are characterised by a shell with an outer, prismatic calcited layer on the right (lower) valve and a byssal notch with ctenolium (at least in their early growth stages).
Propeamusiidae are differentiated by having a byssal notch without ctenolium. The right valve is also with a prismatic calcitic layer.
Species from the family Entoliidae have, like Propeamussiidae a byssal notch without ctenolium but are lacking a prismatic calcited layer on the right valve. They have crossed-lamellar aragonite