. Bulletin of the Natural Histort Museum. Geology series. 62 POPOV, COCKS AND NIKITIN Genus PHACELOORTHIS Percival, 1991 Type species. P. decoris Percival, 1991, from the Quondong Limestone (Caradoc) of New South Wales, Australia. Phaceloorthis? sp. PI. 11, figs 13, 14 Material. One pair of conjoined valves (BC 57531) (L=, W=, T=) from Sample 2538, Kujandysai, near Akchoku Mountain. Description. Shell subequally biconvex, transversely subrect- angular in outline with hinge line somewhat shorter than maximum shell width at mid-length. Anterior margin rectimarginate.
. Bulletin of the Natural Histort Museum. Geology series. 62 POPOV, COCKS AND NIKITIN Genus PHACELOORTHIS Percival, 1991 Type species. P. decoris Percival, 1991, from the Quondong Limestone (Caradoc) of New South Wales, Australia. Phaceloorthis? sp. PI. 11, figs 13, 14 Material. One pair of conjoined valves (BC 57531) (L=, W=, T=) from Sample 2538, Kujandysai, near Akchoku Mountain. Description. Shell subequally biconvex, transversely subrect- angular in outline with hinge line somewhat shorter than maximum shell width at mid-length. Anterior margin rectimarginate. Ventral valve moderately convex in lateral profile with maximum thickness at one-third valve length. Ventral interarea almost orthocline, slightly curved in cross-section with open, narrow triangular delthyrium. Dorsal valve moderately convex with maximum thickness near the mid-valve. Umbonal area with shallow sulcus fading towards mid- valve. Dorsal interarea anacline, planar, linear. Shell surface with 9 low, angular radial plications and sumperimposed finely fascico- stellate ribs 7-9 per 3 mm along the anterior margin. Interior of both valves unknown. Discussion. The interior of this species remains unknown, which makes its generic attribution highly provisional, but there are only a few impunctate mid and late Ordovician orthide genera with fascicostellate ornament and they are mostly related to the family Giraldiellidae. Otherwise fascicostellate ribbing is characteristic of the plectorthid genus Phaceloorthis. This single specimen somewhat resembles Phaceloorthis recondita Popov, Nikitin & Cocks, 2000 from the Otar Member (Upper Caradoc) of the Dulankara Moutains in its general shell shape and size and fascicostellate ornament, but differs in having an orthocline ventral interarea and weak radial plications. Family WANGYUHDAE Zeng, 1989 Genus BOWANORTHIS Percival, 1991 Type species. Bowanorthis fragilis Percival, 1991, Caradoc of New South Wales, Australia. from the
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