. Bulletin of the Natural Histort Museum. Geology series. RHYNCHONELLIDE BRACHIOPOD ISOPOMA TORLEY 161 Isopoma xestum Torley, 1934 Figs 17, 18 1934 Isopoma xestum Torley: 82, pi. 3, figs 16, 17. COMMENT. This species is from the Upper Givetian Massenkalke of Bilveringsen near Iserlohn on the east of the Rhine, Germany. The figured specimens are small and less deep than typical /. brachyptyctum and do not show ribbing. We have studied 11 speci- mens (SMF XVII 347c) and an unregistered specimen, donated by the late Dr Struve, from the Kohlenstein member of the Massenkalk at the Kohlenstein quarr
. Bulletin of the Natural Histort Museum. Geology series. RHYNCHONELLIDE BRACHIOPOD ISOPOMA TORLEY 161 Isopoma xestum Torley, 1934 Figs 17, 18 1934 Isopoma xestum Torley: 82, pi. 3, figs 16, 17. COMMENT. This species is from the Upper Givetian Massenkalke of Bilveringsen near Iserlohn on the east of the Rhine, Germany. The figured specimens are small and less deep than typical /. brachyptyctum and do not show ribbing. We have studied 11 speci- mens (SMF XVII 347c) and an unregistered specimen, donated by the late Dr Struve, from the Kohlenstein member of the Massenkalk at the Kohlenstein quarry in the Iserlohn Bilveringsen area (BD 12785). The sectioned specimen was not well preserved so the internal features remain poorly known and reference of the species to Isopoma remains insecure. STRATIGRAPHIC AND GEOGRAPHIC DISTRIBUTION OF ISOPOMA Twelve species of Isopoma are described or commented upon above; /. aptyctum (Schnur), of supposed Frasnian age, is very poorly known, and we have not been able to study specimens, so we do not describe it here. Of these twelve reasonably established species, eight are from the Eifelian to Givetian of the Middle Devonian, and two (/. alecto (Barrande) and/, nekhoroshevi Bublichenko) from the Pragian and Emsian of the Lower Devonian are doubtfully referred to Isopoma. Two more species (/. ? ren Schmidt and /. xestum Torley), from the upper Givetian might belong to Isopoma, but they are also poorly known. We, therefore, suggest a well established stratigraphical range for Isopoma in the Eifelian and Givetian, with less securely established species in later Lower Devonian rocks. Isopoma appears to be absent from the Devonian of Morocco (Drot, 1964) and Afghanistan (Durkoop, Mensink & Plodowski, 1967; Durkoop, 1970). Brice (1971), however, described specimens from Afghanistan as Kransial cf. subsignata (Reed, 1908), and suggested they are conspecific with specimens from Burma figured by Anderson, Boucot & Johnson (1969) as Uncin
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