136 MR. G. S. WEST ON THE FRESHWATER ALGJE 
120. STAURASTRUM SETIGERUM, Cleve, Bidr. р. 490 (1863) ; Roy & Biss. in 
Ann. Scott. Nat. Hist. (1893) p. 243; ib. (1894) t. 3. fig. 9. 
Var. Nyans2, Schmidle, т Engl. Bot. Jahrb. xxvi. (1898) p. 53, t. 4. 
fig. 8. 
Long. sine acul. 60 u, cum acul. 77 #3 lat. sine acul. 48-52 u, cum acul. 
84-90 ш; lat. isthm. 11 p. 
Victoria Nyanza.—In the plankton, Bukoba (21 Apr. 1905 ; no. 252). 
This Desmid was not uncommon in the plankton of Victoria Nyanza, but 
the specimens observed were decidedly larger than those collected by Stuhlmann 
in 1872 and subsequently described by Schmidle (1898). The var. Nyanse 
appears to differ from the type in the deeper constriction and in the fewer 
number of the more delicate aculei. Even in European specimens, however, 
the number of these delicate aculei is very variable. 
121. STAURASTRUM QUADRANGULARE, Breb. in Ralfs, Brit. Desm. (1848) 
р. 128, t. 34. fig. 11, t. 22. fig. 7. 
Var. ATTENUATUM, Nordst. in. Vidensk. Medd. Naturh. Foren. Kjób. (1870) 
р. 229, t. 4. fig. 44. 
Forma angulis semicellularum compressis, cum spinis duobus supra et spinis 
singulis vel binis infra ; a vertice visis pentagonis, lateribus retusis, angulis 
bi- vel trispinatis. (PI. 6. fig. 6.) 
Long. 25 ш; lat. sine spin. 21-24 д, cum spin. 24-27 д; lat. isthm. 9 y. 
Tanganyika.—In swamp, Mbete (28 Sept. 1904 ; no. 108). 
Lagerheim has recorded a pentagonal form of this variety from Abyssinia 
(vide Nuova Notarisia, 1893, p. 164). The form observed from Tanganyika 
might equally well be regarded as a small pentagonal form of S. angulare, 
W. В. Turn. (in К. Sv. Vet.-Akad. Handl. xxv. (1893) no. 5, p. 130, t. 14. 
По. 17), a species which appears scarcely to be distinct from S. quadrangulare. 
122. STAURASTRUM MONTICULOSUM, Breb. in Menegh. Synops. Desm. (1840) 
p. 226; Ralfs, Brit. Рехт. (1848) p. 130, t. 34. fig. 9. 
Var. BIDENS, var. п. (РІ. 6. fig. 9.) 
Semicellula a fronte visse subreetangulares, verrucis bidenticulatis (vel 
bispinatis) binis supra angulum unumquemque ; a vertice visa quadratze, 
lateribus levissime retusis, angulis bidenticulatis. 
Long. sine dentic. 27 p, cum dentic. 32 №; lat. sine dentic. 22-26 д, cum 
dentic. 26-32 р; lat. isthm. 10 д. 
Victoria Nyanza.—Swampy pools, Bukoba (20 Apr. 1905 ; no. 251). 
This variety differs from S. monticulosum var. bifariwn, Nordst., in the 
absence of the six inferior accessory spinate warts. It closely approaches a 
Desmid described by Raciborski as 5. Libeltii (in Pamietnik matem.-przy. 
Akad. Umiej. Krakow. xvii. (1889) p. 100, t. 7. fig. 12). 
