OF THE THIRD TANGANYIKA EXPEDITION. 147 
Class HETEROKONT AE. 
Order CONFERVALES. 
Family TRIBONEMACEZ. 
Genus OPHIOCYTIUM, Nag. 
ж 
188. OPHIOCYTIUM PARVULUM, (Perty) A. Br. Alg. Unicell. (1855) p. 55.— 
Brochidium parvulum, Perty. 
Crass. cell. 4—5 д. 
Nyasa.—Among weeds and various Algæ, in swamp, Karonga (2 July, 
1904 : no. 34). 
Лаз BACILLARIEZE. 
Order CENTRICA. 
Family MELOSIRACEZ. 
Genus MELOSIRA, Ag. 
189. MELOosIRA NYASSENSIS, O. Müll. in Engl. Bot. Jahrb, xxxiv. (1905) 
p. 285, t. 3. fig. 3. 
Crass. fil. 22-33 р. (Pl. 2. figs. 6, 7 ; PI. 3. figs. 5, 26.) 
Nyasa.—In plankton, Anchorage Bay (9-14 June, 1904 ; nos. 2, 5, 7, 9, 
and 10), and also off Karonga (1 July, 1904 ; no. 30). 
Victoria Nyanza.—In plankton, off Bukoba (20 and 21 Apr. 1905; 
nos. 250 and 252). 
This Diatom was the dominant feature of some of the plankton collections. 
It was described by О. Müller in 1895 from the plankton of Lake N yasa and 
the waters of some of the surrounding areas. It may be regarded as one of 
the numerous forms of Melosira granulata. 
190. Мегозтва GRANULATA, Ztalfs, in Pritch. Infus. ed. 4 (1861), p. 820. 
Nyasa.—In plankton, Anchorage Вау (13 and 14 June, 1904; nos. 
9 and 10). 
Victoria Nyanza.—In plankton, near Bukoba (20 Apr. 1905 ; no. 250). 
Var. ANGUSTISSIMA, О. Müll. 1. с. p. 285, t. 4. fig. 12. 
Crass. fil. 8—45 д. 
Nyasa.—In plankton, Anchorage Bay (9-14 June, 1904; nos. 2, 7, 9, and 
10), and also off Karonga (1 July, 1904 ; no. 30). 
Victoria Nyanza.—In plankton, near Bukoba (21 Apr. 1905 ; no. 252). 
This delicate variety was very abundant in some of the plankton collections, 
and unless cleaned and prepared specially for examination, was difficult to 
recognize as a Melosira. As compared with their diameter, the cells are 
relatively longer than in other forms of M. granulata. 
L2 
