Freshwater Algae of S. of England. By W. & G. S. West. 497 
Yar. minus constricta, semicellulis subquadratis. 
Long. s. spin. 15-17 yu; lat. s. spin. 11 yu ; long. spin. 
5*5-7 yLt; lat. isthm. 7*5 y , ; crass. 8 y. III. 0. 
4. A. Balfsii West. I. Ep. III. Bi., Ew., Pu., Wi. 
5. A. convergens Ehrenb. III. Mp., Th. YI. N. 
Genus Onychonema Wallich. 
1. 0. filiforme (Ehrenb.) Boy et Biss. YIII. G. 
Genus Sphaerozosma Corda. 
1. S. vertelratum (Breb.) Balfs. III. M. 
Yar. latius var. n. (PI. YI. fig. 7.) 
Yar. cellulis latioribus (l§-plo latioribus quam longis), 
sinu angustiori profundiorique, dorso convexiori. 
Long. 15-16 y ; lat. 25-27 y; lat. isth. 5' 5-7 *5 y. 
III. Ew. 
2. S. excavatum Balls. I. Ep. III. C., E., Pu. (with zygo- 
spores), Th. (with zygospores), Wi. YI. N. (with zygospores). 
VII. D., Gp. YIII. T., W. 
3. S. granulatum Boy et Biss. I. Ep. III. Mp., Pu. 
*4. S. Wallichii Jacobs, var. anglicum var. n. (PI. YI. fig. 6.) 
Yar. apicibus semicellularum subarctis, sinu minore, gra- 
nulis 2 vel 3 ad margines laterales semicellarum, cum granulis 
sparsis trans semicellulas irregulariter ordinatis. 
Long. 10-11*5 fi ; lat. 10*5-11 fi\ lat. isthm. 6 yu ; 
crass. 5*5 yu. YI. N. abundant, July 1897. 
Genus Desmidium Ag. 
1. D. cylindrieum Grev. III. Th. YI. N. 
2. D. Swartzii Ag. III. Mp., Th. YIII. H., W. 
Genus Gymnozyga Ehrenb. 
I G. moniliformis Ehrenb. III. Bi., C., Th. YI. N. YIII. 
H., R. 
Genus Hyalotheca Kiitz. 
1. II. mucosa (Dillw.) Ehrenb. III. C. Th. YIII. G. W. 
2. H. dissiliens (Sm.) Breb. Frequent ; zygospores from Bisley, 
Chobham, Esher West-end, and Thursley Commons, Surrey ; 
Keston Common, Kent ; Rough tor Moor, Cornwall. 
Forma tridentula Nordst. III. Ew. YIII. H., L. 
Yar. hians Wolle. II I. Ew. (pure gathering, April 1895). 
*3. H. neglecta Racib. III. Th. YI. N. (with zygospores). 
Long. cell. 28-34*5 yu\ lat. cell. 11*5-13 y, . 
This species was in great abundance from Thursley Common, 
Surrey, and from the New Forest, Hants. It occurs in long filaments, 
