OF THE THIRD TANGANYIKA EXPEDITION, 153 
210. Соссохк:в PrpicuLus, Ehrenb. Infus. p. Ш; W. Sm. Brit. Diat. i. 
p. 21, t. 3. fig. 31. 
Tanganyika.—In plankton, off Niamkolo Island (29 July, 1904 ; no. 86), 
and Kituta Bay (26 Aug. 1904; по. 81). In shallow water, Mbete (29 Sept. 
1904 ; no. 114). 
Family NAVICULACEE. 
Genus NAVICULA, Bory. 
211. NavicvLA ($ Nemum) propucta, W. Sm. Brit. Diat. 1. p. 51. t. 17. 
fig. 144.—N. Iridis var. producta, Van Heurck, Synops. Diat. Belg. p. 104, 
t. 13. fig. 3. 
Nyasa.—In swamp, Karonga (29 June, 1904 ; no. 32). 
212. NavicuLA ($ Nerpium) TaxaaNvncE, sp. п. (PI. 8. fig. 11.) 
Cellula ut in visa aspectu valvulari oblonga cum lateribus levissime con- 
cavis, utroque polis cuneatis et apicibus obtusis ; platea axiali angusta, lineis 
approximatis binis utrobique inter marginem lateralem valvee unumquemque 
et axem centrali, platea centrali transverse dilatata (elliptica); punctis valve 
densissimis et irregulariter ordinatis; striis margines versus visis 10-11 
in 10 p. 
Long. valv. 76-98 ш; lat. 34—10 p. 
Tanganyika.—In plankton, Kituta Bay (25 Aug. 1904; no. 77), near 
Mbete (28 Sept. 1904 ; no. 105), near Kalambo (5 Nov. 1904 ; по. 154), and 
near Baraka (24 Feb. 1905 ; no. 240). 
Pfitzer founded the genus Veidium in 1871 on the general arrangement of 
the cell-contents, and Cleve (1894) has pointed out that the structure of the 
valve is also sufficient to separate the species included in Neidium from 
the rest of the naviculoid Diatoms. М. Tanganyika is on the whole nearest 
to №. Amphigomphus, Ehrenb., but in none of the specimens Т examined were 
the puncte of. the valves arranged in lines. There were а pair of accessory 
longitudinal lines, closely approximate, and running from pole to pole 
between the central line and each margin of the valve. These lines were 
situated rather nearer the outer margin than the median line, and they 
were regularly bent inwards in the cuneate poles. The central area was 
transversely elliptical and the puncte were rather more distinct in its 
immediate vicinity. The striations could only be observed between the 
margins of the valve and the accessory longitudinallines. The area between 
the latter and the sagittal axis (or raphe) was entirely occupied by irregularly 
scattered puncte. 
213. Маме ($ DIPLONEIS) ELLIPTICA, Айг. Васі. (1844) p. 98, t. 30. 
fig. 55.-— №. ovalis, W. Sm. Brit. Diat. i. p. 48, t. 18. fig. 153 a^? 
Nyasa.—In plankton, Anchorage Bay (13 June, 1904 ; no. 9). 
