OF THE THIRD TANGANYIKA EXPEDITION. 117 
This form was not uncommon from the above localities, and to a certain 
extent it combines the characters of C. retusum, (Perty) Rabenh., and С. 
retusiforme, (Wille) Gutw. It has the deep linear constriction of the former, 
but the proportions of the latter. The subrectangular basal angles are 
distinctive. It appears to be a tropical form with a wide geographical 
distribution, and was first described from Sumatra. 
15. COSMARIUM HAMMERI, Reinsch, Sp. Gen. Alg. (1867) p. 115, t. 22 B.I. 
figs. 1-10; W. у 6. 5. West, Brit. Desm. 11. (1905) p. 181, t. 62. figs. 20, 21. 
Long. 30 ш; lat. 22 ш; lat. isthm. 6 р; crass. 11 p. 
Victoria Nyanza.—In swampy pools, Bukoba (20 Apr. 1905 ; no. 251). 
76. CosMARIUM GRANATUM, Breb. in Ralfs, Brit. Desm. (1848) p. 96, t. 32. 
fig. 6: W. & G. S. West, l. c. p. 186, t. 63. figs. 1-3. 
Nyasa.—In pools, Nkata Bay (23 June, 1904; no. 22). In swamp, 
Karonga (2 July, 1904 ; no. 34). 
11. CosMARIUM GALERITUM, JVordst. in Vidensk. Medd. Naturh. Foren. 
Кё}. (1870) p. 209, t. 3. fig. 26. 
Var. RETUsUM, var. п. (Pl. 7. fig. 6.) 
Semicellule lateribus paullo retusis apicem versus et apice leviter retuso. 
Long. 38 ш; lat. 34 u ; lat. isthm. 10 р. 
Nyasa.—In the swampy lake margin, Domira Bay (19 June, 1904; no. 519). 
Victoria Nyanza.—In sheltered bay near Entebbe (1 May, 1905; no. 620). 
The Desmid described and figured by Schmidle from Nyasa (cf. Engl. 
Bot. Jahrb. xxxii. (1903) p. 69, t. 1. fig. 26) as “С. homalodermum var. minor ” 
is most probably identical with this variety. 
78. COSMARIUM NITIDULUM, De Not. Desm. Ital. (1867) p. 42, t. 3. fig. 26 ; 
W. & G. S. West, Brit. Desm. ii. (1905) p. 197, t. 64. figs. 1-3. 
Small form: long. 25 ш; lat. 21 р; lat. isthm. 5 p. 
Tanganyika.—In plankton, Lofu River (5 Oct. 1904 ; по. 124). 
19. (OSMARIUM PSEUDOPYRAMIDATUM, Lund. in Act. R. бос, Sci. Upsal. 
ser. 3, viii. (1871) p. 41, t. 2. fig. 18. 
Victoria Nyanza.—In swampy pools, Bukoba (20 Apr. 1905 ; no. 251). 
Tanganyika.—In swamp, Kituta (28 Aug. 1904 ; no. 79. Also 26 Aug. 
1904; no. 80). 
80. COSMARIUM MONILIFORME, (Turp.) Ralfs, Brit. Desm. (1848) p. 107, 
t. 17. fig. 6. 
Victoria Nyanza.—In plankton, Bukoba (18 Apr. 1905 ; no. 249). 
