WELWITSCH's AFRICAN FRESHWATER ALG«. 237 



Var. LINEARIS Hansg. in Arcliiv. Xatitru-iss. Landesdurchf. B'dhm. 

 Bd. 6, no. 6, 268 (1888). Long. cell. 10-5-17 /x ; lat. cell. 3-5-5 //. 

 Libongo. Ad margines flum. Lifune ; Sept. 1858. No. 204. 



6. Tetraedron Kiitz. (1845). 



1. T. MINIMUM (A. Br.) Hansg. in Hedwiffia, 1888, 131. Poly- 

 ediium minivuim A. Br. in Rabenli. FL Euioj). Air/, iii. 62. Diam. 

 9'5-ll-5 /a; crass. 55 ji. 



From the references given under the name T, viiniinuin in his 

 paper in Hedwiijia it would appear that Hausgirg was under the 

 erroneous impression that Brauu described this plaut in Rabh. FL 

 Europ. Alg. as a Tt'trciedron. 



Libongo. Ad margines flum. Lifune ; Sept. 1858. No. 204. 



2. T. tropicum, sp. n. T. mediocre, trigonum, lateribus levis- 

 sime concavis, angulis rotundatis, membrana crassa et scrobiculata, 

 scrobiculis magnis et hexagonis, propter scrobiculos magnos con- 

 fertos margo asperus videtur ; a latere visum subrhomboideo-elHp- 

 ticum. Diam. 27-30 /x ; crass. 16 /x. 



Libongo. Ad margines flum. Lifune ; Sept. 1858. No. 204. 



This should be compared with T. retuulatum (Reinsch) Hansg. ; 

 in the latter species the membrane is not nearly so thick, and the 

 scrobiculations are so large that the superficial part of the membrane 

 only consists of a fine reticulation. 



3. T. tetragonum (Nag.) Hansg. I.e. (1888). PoJijedrium tetra- 

 fjomm Nag. Gatt. einz. Aly. 84, t. iv. B, fig. 2 (1819). 



Var. iNERME (Wille in Bihcnifj t. K. Sv. Vet.-Akad. Handl. Bd. 8, 

 no. 18 (1884), 12, t. i. f. 25). Diam. 21 //; crass. 9-5 /x. 



Huilla. In uliginosis editioribus prope Humpata, Empalanca 

 et Lopollo ; May 1860. No. 15. 



4. T. pusiLLUM (Wallich). Micrasterias puailla Wallich in Ann. 

 May. Nut. Hist. ser. iii. vol. v. 281, t. xiii. fig. 13 (1860). Stauro- 

 phaniim pusillwn W. B. Turn, in A'. Sr. Vet.-Akad. Handl. Bd. 25, 

 no. 5, 159, t. XX. f. 22 (1893). 



Var. ANGOLENSE, var. n. Var. cellulis subtortis vel irregulariter 

 tetrahedricis, angulis profundius divisis, divisionibus 2 (vel 3) late 

 divaricatis, spiuiformibus sed tubularibus pa^ne ad apicem. Diam. 

 sine spin. 19-23 /x, cum spin. 27-36 /x ; crass. 85 /x. 



Libongo. Ad margines flum. Lifune ; Sept. 1858. No. 204. 



We see no reason for Turner's genus Staurophanuni, as no clear 

 line of demarcation can be drawn between those species which it 

 would include and those referable to Tetraedron. Indeed Tetraedron 

 pmillum is very closely connected through its var. ani/oleusa with 

 T. lobidatinn (Nag.) Hansg. 



5. T. RKGULARE Kiitz. Phyc. Germ. 129 (1845). Polyedrium tetra- 

 edrienm Niig. Gatt. einz. Aly. 84, t. iv. B, fig. 3 (1849). Diam. 27 /x. 



Pungo Andongo. In stagnis prope Aubilla (Condo) ; March 

 1857. No. 177. 



Forma majus Reinsch in Ahhandi. XatnrJiist. Gesellsch. Xurnberq, 

 Bd. 3, H. 2, 77, t. v. fig. 2 (1866). Diam. 49 /i. 



Libongo. Ad margines Hum. Lifune; Sept. 1858. No. 201. 



