OF THE THIRD TANGANYIKA EXPEDITION. 155 
Tanganyika.—In plankton, Kituta Bay (26 Aug. 1904; no. 81), and 
off Kirando (1 Dec. 1904 ; no. 175). 
222. NAVICULA RHYNCHOCEPHALA, Айг. Вас. (1844) t. 30. fig. 35 ; 
Donkin, Brit. Diat. p. 38, t. 6. fig. 4. 
Nyasa.—In plankton, Anchorage Bay (June 1904 ; nos. 9 and 10). 
Tanganyika.—In plankton, Kituta Bay (26 Aug. 1904; по. 81), near 
Mbete (28 Sept. 1904; no. 105), and near Chamkaluki (15 Nov. 1904 ; 
no. 160). In swamp, Toa (10 Jan. 1905 ; no. 208). 
223. NAVICULA DISTINCTA, sp. n. 
Minuta ; cellula ut in visa aspectu valvulari late elliptica, polis rotundatis 
vel subacute rotundatis ; striis validis, distinctis et glabris, 8 in 10 р, radiatis, 
in parte mediana striis brevibus 2 vel 3 cum striis multe longioribus 
alternantibus. 
Long. 20-24 ш ; lat. 16-17 p. 
Tanganyika.—In plankton, near Kala (19 Nov. 1904 ; no. 170.) 
This small species is distinct by reason of its broadly elliptical valves and 
the conspicuous striations. There are in all 17 or 18 striations along each 
side of the valve, markedly radiating in disposition, and reaching close up to 
the sagittal line or raphe. Two or three of the median striations are relatively 
short, extending only about halfway from the margin of the valve to the 
sagittal line. These short striations do not occur next each other, but alternate 
with those of maximum length. The striations appear to be perfectly 
smooth. 
224. NAVIOULA GasTRUM, Kiitz. Вас. (1844) p. 94; Donkin, Brit. Diat. 
p. 22, t. 3. fig. 10; Van Heurck, Synops. Diat. Belg. р. 81, t. 8. figs. 25, 21. 
Nyasa.—In plankton, Anchorage Bay (June 1904 ; nos. 9 and 10). On 
rocks, Deep Bay (25 June, 1904 ; no. 26). 
Tanganyika.—In plankton, Kitutu Bay (26 Aug. 1904; по. 81), near 
Niamkolo (7 Sept. 1904 ; no. 88), near Mbete (28 Sept. 1904 ; no. 105), 
Lofu (6 Oct. 1904 ; no. 120), near Kala (19 Nov. 1904 ; no. 170), and near 
Kirando (1 Dec. 1904 ; no. 175). 
From no. 175 some very large forms were observed: length 64 p; 
lat. 28 p. 
225. NAVIOULA DICEPHALA, W. бт. Brit. Diat. i. р. 87, t. 17. fig. 157. 
Nyasa.—In swamp, Karonga (2 July, 1904 ; no. 33). 
Tanganyika.—In rain-water pool on large rock near the shore, Utinta 
(6 Dec. 1904 ; no. 1806). 
226. NaAvICULA ($ PINNULARIA) INTERRUPTA, W. Sm. l. c. ii. p. 96; Cleve, 
Synops. Navic. Diat. ii. (1895) p. 76.—N. bicapitata, Lagerst. Pinnularia 
biceps, Greg. 
