FIGURES 69–81. Some central raphe fissure ending shapes in Gyrosigma and Pleurosigma species. No scale bars added, as not relevant in this context. Fig. 69. Gyrosigma attenuatum (Kützing) Cleve. Fig. 70. G. peisonis (Grunow) Hustedt. Fig. 71. G. littorale (W. Smith) Griffith et Henfrey. Fig.72. G. tenuissimum (W.Smith) Griffith & Henfrey. Fig.73. G. obtusatum (Sullivant et Wormley) Boyer. Fig. 74. Pleurosigma aff. normanii Ralfs in Pritchard. Fig. 75. P. elongatum W. Smith. Fig. 76. P. frenguellianum Sunesen, Sterrenburg & Sar. Fig. 77. P. perlucidum Sar, Sterrenburg & Sunesen. Fig. 78. P. patagonicum (Ferrario & Sar) Sterrenburg & Sar. Fig. 79. P. indicum Simonsen. Figs 80, 81. Different shapes seen in a single slide of P. aff. normanii Ralfs in Pritchard.