10 Surirella cruciata A. S. 127 11 Surirella gracilis Grun. 127 12-13 Surirella amphioxys Wm. Sm. 124 [Illustration: PLATE 35] PLATE 36 SURIRELLA--Continued 1 Surirella elegans Ehr. 125 2 Surirella robusta Ehr. 124 3 Surirella febigerii Lewis 128 4 Surirella gemma Ehr. 125 5 Surirella guatimalensis Ehr. 126 6 Surirella panduriformis Wm. Sm. 126 7-9 Surirella pinnata Wm. Sm. 126 8 Surirella angusta Kuetz. 127 [Illustration: PLATE 36] PLATE 37 CYMATOPLEURA 1 Cymatopleura elliptica (Bréb.) Wm. Sm. 129 2 Cymatopleura elliptica forma spiralis 129 3-4 Cymatopleura marina Lewis 129 CAMPYLODISCUS 5 Campylodiscus hibernicus Ehr. 130 6 Campylodiscus echeneis Ehr. 130 [Illustration: PLATE 37] PLATE 38 1 Amphora gigantea var. fusca A. S. 65 2 Meloseira crenulata (Ehr.) Kuetz. 15 3-4 Licmophora baileyi (Edw.) Grun. 40 5 Coscinodiscus polyacanthus Grun. 22 6-7 Ditylum intricatum (West) Grun. 30 8 Pyxidicula cruciata Ehr. 19 9 Gyrosigma scalproides (Rab.) Cl. 76 10 Coscinodiscus asteromphalus var. omphalantha (Ehr.) Grun. 23 11 Rhabdonema minutum Kuetz. 36 12 Gyrosigma kuetzingii (Grun.) Cl. 76 13 Gyrosigma prolongatum (Wm. Sm.) Cl. 76 14 Cymbella parva (Wm. Sm.) Cl. 61 15 Gomphoneis herculaneum (Ehr.) Cl. (zone view) 70 16 Cymbella ventricosa Kuetz. 62 17-18 Eunotia sp. (abnormal?) 54 [Illustration: PLATE 38] PLATE 39 1 Nitzschia spectabilis var. americana Grun. (zone view) 122 2 Nitzschia panduriformis Greg. 117 3 Hantzschia amphioxys (Ehr.) Grun. 113 4 Hantzschia amphioxys var. major Grun. 114