Each of a series of Cambrian deposits, mainly micaceous flagstones and slates (originally in North Wales), containing abundant fossils of lingulate brachiopods; usually in plural.
Origin
Mid 19th century.
Definition of Lingula flag in US English:
Lingula flag
noun
Geology
Each of a series of Cambrian deposits, mainly micaceous flagstones and slates (originally in North Wales), containing abundant fossils of lingulate brachiopods; usually in plural.