Article: Isorthis and Salopina (Brachiopoda) in the Ludlovian of the Welsh Borderland
Examination of the enteletacean brachiopod members of the faunal assemblages now used in British Ludlovian stratigraphy (Holland, Lawson, and Walmsley 1963) and comparison with a large collection of Silurian and Lower Devonian brachiopods from many parts of the world, reveals that the species commonly determined as Dalmanella lunata (J. de C. Sowerby) and D. orbicularis (J. de C. Sowerby), have not yet been found, (though sometimes recorded), from areas outside Britain. However, one of the new species of Isorthis here described has a wide distribution in Britain and occurs in North America (Maine and New Brunswick) and South America (Venezuela). Salopina Boucot is emended and Salopina lunata is described, figured and distinguished from S. submedia (McLearn), which was figured as S. lunata by Boucot 1960, from New Brunswick. Isorthis Kozlowski is emended and Orthis orbicularis J. de C. Sowerby together with two new species (I. amplificata and I. clivosa), and two new subspecies (I. scuteformis scuteformis and I. scuteformis uskensis), from the Welsh Borderland and a new, related species (I. slitensis) from Gotland, are assigned to Isorthis and described and figured.