9 Caloneis trinodis (Lewis) var.? 81 10 Caloneis powellii (Lewis) Cl. 83 18 Caloneis formosa (Greg.) Cl. 82 NEIDIUM 11 Neidium affine (Ehr.) Pfitzer 83 12 Neidium affine var. genuina forma minor Cl. 83 13 Neidium affine var. amphirhyncus (Ehr.) Cl. 83 14 Neidium amphigomphus (Ehr.) Pfitzer. 83 15 Neidium hitchcockii (Ehr.) Cl. 84 16 Neidium productum (Wm. Sm.) Cl. 83 17 Neidium iridus (Ehr.) Cl. 84 [Illustration: PLATE 21] PLATE 22 PLEUROSIGMA 1 Pleurosigma strigosum Wm. Sm. 74 2 Pleurosigma rigidum Wm. Sm. 75 3 Pleurosigma angulatum (Quekett) Cl. 74 4 Pleurosigma obscurum Wm. Sm. 74 5 Pleurosigma formosum Wm. Sm. 73 6 Pleurosigma naviculaceum Bréb. 74 7 Pleurosigma æstuarii Bréb. 74 8 Pleurosigma virginiacum H. L. Smith 74 [Illustration: PLATE 22] PLATE 23 GYROSIGMA 1 Gyrosigma strigilis (Wm. Sm.) Cl. 76 2 Gyrosigma balticum (Ehr.) Cl. 75 3 Gyrosigma hippocampus (Ehr.) 75 4 Gyrosigma simile (Grun.) 76 5 Gyrosigma acuminatum (Kuetz.) Cl. 76 6 Gyrosigma scalproides (Rab.) Cl. 76 7 Gyrosigma parkeri var. stauroneioides Grun. 75 8 Gyrosigma spencerii var. nodifera Grun. 76 9 Gyrosigma fasciola (Ehr.) Cl. 77 [Illustration: PLATE 23] PLATE 24 NAVICULA 1 Navicula maculata (Bail.) Cl. 90 2 Navicula prætexta Ehr. 92 3 Navicula latissima Greg. 90 4 Navicula irrorata Grev. 93 5 Navicula latissima var. elongata (Pant.) Cl. 91 6 Navicula fuchsii Pant. 91 [Illustration: PLATE 24] PLATE 25 NAVICULA 1 Navicula tumida (Bréb.) Cl. 99 2 Navicula brasiliensis var. bicuneata Cl. forma constricta. 92