. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. Fig. 19. Leptothyrella cf. ignota (Muir-Wood, 1959), SAM-A25482, SM 129. A. Dorsal view of conjoined valves. B. Interior view of pedicle valve. C-D. Ventral and lateral views of brachial valve interior showing brachidium. All x8. Dimensions (mm) Length Width SAM-A25482 2,5 1,8 Discussion The inwardly directed crura, high pillar-Uke septum, wide foramen with incipiently developed deltidial plates of this little specimen all point to an early growth stage of a terebratellacean. However, the poorly know
. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. Fig. 19. Leptothyrella cf. ignota (Muir-Wood, 1959), SAM-A25482, SM 129. A. Dorsal view of conjoined valves. B. Interior view of pedicle valve. C-D. Ventral and lateral views of brachial valve interior showing brachidium. All x8. Dimensions (mm) Length Width SAM-A25482 2,5 1,8 Discussion The inwardly directed crura, high pillar-Uke septum, wide foramen with incipiently developed deltidial plates of this little specimen all point to an early growth stage of a terebratellacean. However, the poorly known Leptothyrella ignota (Muir-Wood) from off Zanzibar and the Gulf of Aden is remarkably similar, although Muir-Wood's specimens, which the author has examined, are larger at 5 mm length. Both forms are coarsely punctate and have the same overall shell outline with gently convex valves and rectimarginate anterior commissure. Both have an open delthyrium flanked by extremely narrow deltidial plates and floored by a pedicle collar that extends almost the full length of the delthyrium. The brachial valve of L. ignota has a high, plate-like median septum, which does not continue posteriorly into the notothyrial cavity; the crura are slender and curved; the cardinal process is minute. Any differences between L. ignota and the shefl described here can be accounted for by the larger size and presumably more adult nature of L. ignota, by which stage the tiny cardinal process has developed as have the points of attachment of the descending branches to the median septum. Otherwise both forms are so similar that they must be regarded as being very closely related. ACKNOWLEDGEMENTS I wish to thank the Director of the South African Museum for allowing me the opportunity to study the Meiring Naude brachiopods. Thanks are also due to Professor A. D. Wright for permitting the author to use the facilities in the Department of Geology, Queen's University, Belfast, where much of the present study
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