Freshwater Algse of 8. of England. By W. & G. S. West. 493 
Yar. divergens Nordst. IY. Ks. (with zygospores). 
Yar. maximum West. I. Ep. 
9. 8. (JMearii Arch. III. Pu., Th. VIII. II. 
10. 8. sibiricum Borge, forma trigona West and G. S. West. 
III. Dj. 
11. 8. lanceolatum Arch. III. Th., abundant. YI. N., abun- 
dant (with zygospores). VIII. H. 
Yar. compression West. YI. N. 
12. 8. corniculatum Lund. III. Th. (with zygospores). YI. N. 
13. S. TRACHYTITHOPHORUM Sp. n. (PI. YI. fig. 22.) 
S. parvum, tam longum quam latum, profunde constrictum, 
sinu aperto et subrectangulari ; semicellulm late ellipticse, 
polis mamillatis et seorsum curvatis, annulis duobus granulo- 
rum minutorum circa polum unumquemque ; a vertice visae 
triangulares, lateribus subrectis (levissime convexis), angulis 
leyiter productis, cum annulis duobus granulorum minutorum. 
Long. 30-34 //,; lat. 29-32 • 5 //, ; lat. isthm. 10*5- 
11-5 /a. III. Th. 
This species seems to be quite distinct from any other. 
14. 8. lunation Baits. I., Ep. Y. Go. YI. N. 
Var. subarmatum West. I. Ep. 
*15. 8. tunguscanum Boldt. III. Pu. 
16. 8. denticulatum (Nag.) Arch. I. Ep. 
17. 8. Avicula Breb. VII. D. VIII. G. 
Yar. subarmatum (Wolle) West. I. Ep. VI. N. 
18. 8. furcatum (Ehrenb.) Breb. (8. spinosum Balfs). III. Th. 
VIII. H. 
Yar. subsenarium W. VII. D. 
19. 8. armigerum Breb. ($. pseudofurcigerum Beinsch). III. 
Bi., Pu., We. YI. N. VII. D., Gp. 
20. 8. arcuatum Nordst. T. Ep. VI. N. YIII. G. 
21. S. Beinschii Roy. III. C., Dj., E., Th. YIII. B. 
22. S. rostellum Roy et Biss. YI. N. 
Yar. erostellum yar. n. (PL YI. fig. 18.) 
Yar. minor, profundius constricta, spina magna prope 
constrictionem nulla ; a vertice visum triangulare, 
angulis rotund atioribus. 
Long. s. spin. 19-5/4; lat. s. spin. 19 '5/x; lat. 
isthm. 6*5 ya. III. Th. 
Although the character giving the name to this species is absent, 
still the number, size, and arrangement of the spines is exactly the 
same ; the form of the semi-cells also w T onld be just the same if the 
constriction were less deep. 
23. 8. Hystrix Balfs. III. Di., Dj., Th. 
24. 8. teliferum Balfs. III. Bi., Pu., Th. VII. D., Gp. VIII. 
G., H., L., W. 
