FIGURES 58–64. Tursiocola costata. Type population, SEM. 58. External view of entire valve showing drawn out rostrate apices, asymmetric valve face, bent axial area, diamond-shaped central area and narrow stauros. 59. External view of central area showing deflection of proximal raphe ends. 60. External view of apparently bifurcated distal raphe end. 61. External oblique view of entire valve with attached cingulum showing raised interstriae costae and convergent striae on valve face, raised central area, distinct valve mantle and 2 copulae, each with 1 row of pores. 62. Entire frustule in girdle view showing raised interstriae costae and cingulum with 2 copulae, each with a single row of pores adjacent to the valve margin. 63. Detail of valve center and cingulum in oblique view showing transitions between valve face, mantle and margin. 64. Detail of external valve center in oblique view showing raised interstriae costae, round areolae and narrow stauros. Scale bars: 58, 61–62 = 5 μm; 59–60, 63–64 = 1 μm.