. Bulletin of the British Museum (Natural History). LOWER ORDOVICIAN BRACHIOPODA 23 In addition to the acrotretaceans discussed here, the Bryn Glas Limestone residues have yielded miscellaneous faunal elements including the 'acutely conical valves' (BB 94056-7) illustrated (Figs 57-58). These exceptionally conical valves, although exhibiting no recognizable protegular ornament, show a discernible change in cone slope near the apex and a well-developed apical foramen. With our present imperfect knowledge of acrotretacean faunas we tentatively consider that these valves may also be related to th
. Bulletin of the British Museum (Natural History). LOWER ORDOVICIAN BRACHIOPODA 23 In addition to the acrotretaceans discussed here, the Bryn Glas Limestone residues have yielded miscellaneous faunal elements including the 'acutely conical valves' (BB 94056-7) illustrated (Figs 57-58). These exceptionally conical valves, although exhibiting no recognizable protegular ornament, show a discernible change in cone slope near the apex and a well-developed apical foramen. With our present imperfect knowledge of acrotretacean faunas we tentatively consider that these valves may also be related to the Torynelasmatinae. Genus indet Material and Discussion. An assemblage of small acrotretids recovered from basal G. teretiiisculiis shales exposed just east of Welfield Lodge (SO 044528) represents the first authentic record of this order from the Builth area. The specimens, SM A. 105827-36, exhibit acutely conical pedicle valves about twice as deep (up to 3'5 mm) as long (1-5-2-Omm) and subcircular slightly convex brachial valves with a median septum of unknown profde. They are unlike Conolreta or Apsotreta from the Shelve area (Williams 1974) and may ultimately prove to be more closely related to the Torynelasmatinae. Superfamily DISCINACEA Gray, 1840 Family TREMATIDAE Schuchert, 1893 Genus TREMATISSharpt, 1848 Trematis evansi [Addison MS] sp. nov. (Figs 59a-c) Diagnosis. Subcircular, biconvex Trematis with pedicle notch about three-fifths as long as valve, situated in broad posteromedian sector; ornament quincuncial with 12 concentric pit rows betwen 4 and 5 mm anteromedially of dorsal umbo and 7 pits per mm in each row at this point. Name. For D. C. Evans, who in 1906 published his pioneering work on the Ordovician rocks of western Carmarthenshire. Description. Subcircular biconvex Trematis with valves slightly wider than long and about one-quarter to one-fifth as deep as long; pedicle valve with broad posteriomedian sulcus extending from the apex, just anterior to the mid-
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