Gesoriacorostrum , a new Middle Frasnian rhynchonellid (brachiopod) genus from Boulonnais (N France)

Gesoriacorostrum n. gen., type species G. boloniense (d'Orbigny 1850), is described from the middle Frasnian of Boulonnais (N France). On account of the very brief original description, and its scarcity, the species has been the subject to various interpretations and so is here redescribed. This is based only on the lectotype of the species and four specimens very like it from the type locality.