. Bulletin of the Natural Histort Museum. Geology series. Fig. 15 Isopoma orthoglossa (Torley). Lectotype; dorsal, ventral, anterior and lateral views (with ventral valve uppermost); Flinzkalk, Givetian, Iserlohn, SMF XVII 1164a, x (from Schmidt, 1951: pi. 1, fig. 6). Isopoma nekhoroshevi Bublichenko, 1974 1974 Isopoma nekhoroshevi Bublichenko: 73, text-fig. 9; pi. 2, fig. 9. Comment. This species is from the Emsian of the Rudnogo Altai, Ural Mountains, Russia. The specimens are small, the ventral sulcus starts near the ventral umbo and ribbing is confined anteriorly, associated with the f
. Bulletin of the Natural Histort Museum. Geology series. Fig. 15 Isopoma orthoglossa (Torley). Lectotype; dorsal, ventral, anterior and lateral views (with ventral valve uppermost); Flinzkalk, Givetian, Iserlohn, SMF XVII 1164a, x (from Schmidt, 1951: pi. 1, fig. 6). Isopoma nekhoroshevi Bublichenko, 1974 1974 Isopoma nekhoroshevi Bublichenko: 73, text-fig. 9; pi. 2, fig. 9. Comment. This species is from the Emsian of the Rudnogo Altai, Ural Mountains, Russia. The specimens are small, the ventral sulcus starts near the ventral umbo and ribbing is confined anteriorly, associated with the fold and sulcus. The hinge plate appears to be divided (Bublichenko, 1974: text-fig. 9) and the lack of a median septum is normal for the genus. Isopoma orthoglossa (Torley, 1908) Fig 15 1908 Camarophoria orthoglossa Torley: 29, pi. 3, figs 20, 21, pi. 4, figs 1-3. 1951 Isopoma orthoglossa (Torley); Schmidt: 87, pi. 1, figs 6a-d. Comment. Schmidt (1951) redescribed this species from the Flinzkalk (Upper Givetian) in the IserlohnT^etmathe area on the east side of the river Rhine, Germany. The lectotype (Schmidt, 1951: pi. 1, fig. 6) is comparable to the wide Givetian specimens of Isopoma brachyptyctum. No information on internal structures was given by Schmidt. Further work on this species and the wider form of /. brachyptyctum from the Upper Givetian of the eastern Rhine area is needed to establish their relationships. We have studied two speci- mens from Bilveringsen (SMF XVII 478a), but have not been able to prepare sections. Isopoma ovale Xian Si-yan & Jiang Zong-long, 1978 1978 Isopoma ovale Xian & Jiang: 289, pi. 106, fig. 13. Comment. Isopoma ovale is from the lower part of the Dushan Formation (Givetian), Dongyao, Xiasi, Dushan County, Guizhou, China. Externally this species somewhat resembles the wider forms of/, brachyptyctum found in the Upper Givetian strata of Germany. Xian & Jiang (1978: 289) record 'dental plates fused with the wall of shell'. However,
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