162 MR. С. $. WEST ON THE FRESHWATER ALGE 
259, RHOPALODIA GRACILIS, 0. Mill. in Engl. Bot. Jahrb. xxii, (1895) 
р. 63 ; А. Schm. Atlas Diat. t. 255. figs. 33-21. 
Tanganyika.—In_ plankton, off Niamkolo Island (29 July, 1904 ; no. 36) 
and off Kalambo (5 Nov. 1904 : no. 154). 
Var. UNDULATA, О. Müll. in Hedwigia, xxxvi. (1905) p. 163, t. 1. fig. 17. 
Nyasa.—In plankton, Anchorage Bay (по. 1) and off Vahambwera Point 
(24 June, 1904 ; no. 24). 
Var. IMPRESSA, O. Mill. ; А. Schm. Atlas Diat. t. 255. figs. 28-32. 
Nyasa.—Swampy lake margin, Domira Bay (19 June, 1904 ; no. 579). 
260. RHOPALODIA VERMICULARIS, Ô. Müll. l. e. p. 67, t. 1. figs. 34-39, t. 2. 
figs. 10, 11, 14 ; А. Schm. Atlas Diat. t. 256. figs. 17-19. 
Nyasa.—In plankton, Monkey Bay (17 June, 1904 ; no. 14). On rocks, 
Deep Bay (25 June, 1904 ; no. 26). 
Victoria Nyanza.—Among Utricularia, near Entebbe (1 May, 1905; no. 620). 
This species is commonly attached by thick gelatinous stalks and occurs in 
dense clusters. It was observed forming thick, yellow-brown, matted masses 
on the back of a beetle (Limnogeton) on the lake shore, Karonga, Nyasa. 
Family NITZSCHIACEZS. 
Genus NITZSCHIA, Hass. ; em. Grunow. 
261. NrrzscHIA TRYBLIONELLA, Hantzsch, in Rabenh. Alg. по. 980 (1860). 
Var. LITTORALIS, (Grun.) Van Heurck.—N. littoralis, Grun. 
Tanganyika.— In plankton, near Niamkolo (7 Sept. 1904 ; no. 88). 
262. Nivzscata LawcETTULA, О, Mill. in Engl. Bot. Jahrb. xxxvi. (1905) 
p. 175, t. 2. fig. 15. 
Long. 46-48 р; lat. 10-11 p ; punct. carin. 6 in 10 р; striis 13 in 10 р. 
Nyasa.—In plankton, Anchorage Bay (June 1904 ; nos. 9 and 10). 
263. NITZSCHIA DISSIPATA, (Kütz.) Grun. іп Cleve $ Grun. Arct. Diat. 
р. 90 (1880).—Synedra dissipata, АИ. 
Var, MEDIA, Hantzsch. 
Tanganyika.—In plankton, near Sumbu (18 Oct. 1904 ; no. 138). 
264. NITZSCHIA TUBICOLA, Grun. l. с. р. 97 ; Van Heurck, Synops. Diat. 
Belg. (1885) t. 69. fig. 14. 
Long. 69 ш; lat. Тр ; punct. carin. 7 in 10 р. 
Tanganyika.—In plankton, off Niamkolo Island (29 July, 1904 ; no. 36) 
and near Kala (19 Nov. 1904 : no. 170). 
