. Bulletin of the British Museum (Natural History), Geology. 45& CARADOCIAN BRACHIOPOD FAUNAS OF THE BALA DISTRICT costella thickened to give a narrowly segmented appearance ; 3 to 5 impersistent rugae commonly developed postero-laterally disposed at acute angles to hinge-line and extending antero-medianly through a sector of about 20-250 in each postero- lateral area ; ventral interarea apsacline, delthyrium relatively narrow, pseudo- deltidium absent in adult shells, dorsal interarea anacline, chilidium large and convex; teeth small, elongated and ankylosed with widely divergent dental l
. Bulletin of the British Museum (Natural History), Geology. 45& CARADOCIAN BRACHIOPOD FAUNAS OF THE BALA DISTRICT costella thickened to give a narrowly segmented appearance ; 3 to 5 impersistent rugae commonly developed postero-laterally disposed at acute angles to hinge-line and extending antero-medianly through a sector of about 20-250 in each postero- lateral area ; ventral interarea apsacline, delthyrium relatively narrow, pseudo- deltidium absent in adult shells, dorsal interarea anacline, chilidium large and convex; teeth small, elongated and ankylosed with widely divergent dental lamellae to form pair of hollow, acutely triangular structures extending anteriorly for about one- twelfth the length of pedicle valve ; ventral muscle field large, splayed, subcircular extending anteriorly for about one-half the length of pedicle valve and about four-fifths as long as wide with elevated radiating ridges separating each diductor scar into as many as 5 distinct lobes in adult shells, pedicle callist well developed, passing into broad, medianly indented ridge extending anteriorly for about one- seventh the length of pedicle valve, adductor scars lanceolate, commonly indistinct and impressed anterior of ridge ; cardinal process lobes with splayed posterior faces, not greatly elevated above anchor-shaped notothyrial platform, median septum between lobes commonly vestigial ; socket ridges elongate and ankylosed to lateral extensions of notothyrial platform, dorsal adductor impressions vague, divided by pair of narrowly divergent ridges ; ventral pallial sinus pattern saccate with up to 4 pairs of arcuate branches arising from subjacent vascula media ; dorsal pattern Fig. 13. The ventral internal mould of Macrocoelia expansa (J. de C. Sowerby), X2-5 approx., showing the pallial sinus pattern : gg, vascula genitalia ; m, vascula Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability -
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