. Bulletin of the Natural Histort Museum. Geology series. UPPER ORDOVICIAN BRACHIOPODS FROM KAZAKHSTAN 73 sulcus with a single accentuated primary rib originating in the umbonal area. The coarsely ribbed radial ornament, well defined dorsal median fold and ventral sulcus resembles numerous species of Plectocamara described by Cooper (1956) from the Caradoc of North America, but there is no evidence of the presence of alate plates in the former genus. Family PARALELLELASMATIDAE Cooper, 1956 Genus SCHIZOSTROPHINA Fu, 1982 Type species. Schizostrophina margarita Fu, 1982, from the Jinhe Formation
. Bulletin of the Natural Histort Museum. Geology series. UPPER ORDOVICIAN BRACHIOPODS FROM KAZAKHSTAN 73 sulcus with a single accentuated primary rib originating in the umbonal area. The coarsely ribbed radial ornament, well defined dorsal median fold and ventral sulcus resembles numerous species of Plectocamara described by Cooper (1956) from the Caradoc of North America, but there is no evidence of the presence of alate plates in the former genus. Family PARALELLELASMATIDAE Cooper, 1956 Genus SCHIZOSTROPHINA Fu, 1982 Type species. Schizostrophina margarita Fu, 1982, from the Jinhe Formation (Caradoc), northwest China. DIAGNOSIS (emended). Shell equally biconvex with parasulcate anterior commissure; shallow ventral median sulcus and dorsal median fold originating in umbonal area; radial ornament of variably developed coarse angular ribs in posterior half of the shell; ventral interior with delicate teeth and spondylium supported posteriorly and free anteriorly; dorsal interior with separated outer plates, slightly diverging distally, and well-defined brachial processes. Discussion. Schizostrophina was erected originally by Fu (1982) without proper illustrations and detailed description of the interior in the type species. However, the very distinctive exterior morphology of the shell, which is unique in late Ordovician syntrophiidines, leaves no doubt that the Kazakh shells from the Anderken Formation belong to the same genus and species. Their internal morphology confirms the original assignment of the genus to the Paralellel- asmatidae and suggests a close affinity to Paralellelasma, but Schizostrophina lacks the radial capillae and the characteristic trun- cated margins of the ribs along the commissure of the former genus. Another difference is the parasulcate anterior commissure. Schizostrophina margarita Fu, 1982 PI. 14, figs 2-27; Fig. 20 1982 Schizostrophina margarita Fu: 132, pi. 37, fig. 5. 1982 Schizostrophina shaanxiensis Fu: 133, pi. 37, fig. 6. Materi
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