Annals of the South African MuseumAnnale van die Suid-Afrikaanse Museum . B /. Fig. 8. Steinmanella holubi (Kitchin), x 1. A-B. Lateral and dorsal views of an aberrantindividual in which the flank costae are interrupted anteroventrally. C. Lateral view of a frag-mentary left valve from the Mngazana Formation of Transkei, in the South African Dorsal and lateral views of a juvenile, PEM-1208c. LOWER CRETACEOUS TRIGONIOIDA FROM THE ALGOA BASIN 19 growth striae and the median row of tubercles. These are replaced by irregular,transverse growth rugae in maturity. Flank ornament comprises
Annals of the South African MuseumAnnale van die Suid-Afrikaanse Museum . B /. Fig. 8. Steinmanella holubi (Kitchin), x 1. A-B. Lateral and dorsal views of an aberrantindividual in which the flank costae are interrupted anteroventrally. C. Lateral view of a frag-mentary left valve from the Mngazana Formation of Transkei, in the South African Dorsal and lateral views of a juvenile, PEM-1208c. LOWER CRETACEOUS TRIGONIOIDA FROM THE ALGOA BASIN 19 growth striae and the median row of tubercles. These are replaced by irregular,transverse growth rugae in maturity. Flank ornament comprises c. 16 distant rows of prominent nodes that curveslightly to the anterior, the nodes becoming more crowded ventrally with anoccasional intercalated row along the anteroventral margin. The interspaces areslightly narrower than the rows of nodes. Along the ventral margin of matureshells, the tubercles tend to become elongated and may coalesce to form concen-tric growth rugae. In many individuals, the distal terminations of the ribs curvestrongly to the anterior. Ornamentation
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Keywords: ., bookauthorsouthafr, bookcentury1800, bookdecade1890, bookyear1898
