170 
THE JOURNAL OE BOTANY 
A. convergens Ehrenb. Loc. 10, 27, 5G. Distr. General, 
forma triangularis n. f. Semicellulis a termino visis triangu- 
laribus : cetera ut in typo. 
The relationships of A. convergens are difficult to determine. 
The occurrence of spineless forms indicates a relationship with Cos- 
mar ium depressuni ( Naeg.) Lund ; but the trimerous form noted 
here might equally well be placed in Staurastrum. Had the specimens 
Arthrodesmus convergens Ehrenb. f. triangularis Crow, n. f. 
End and side views of semicell. 
occurred isolated, it would have been advisable to describe them as 
species of the latter genus; but they were mixed up with perfectly 
normal dimerous specimens of A. convergens . Trimery has previously 
recorded for A. triangularis form*, sometimes regarded as forms of 
A. Incus. Loc. 27. 
A. subulatus Kuetz. Loc. 32. Distr. Chiefly tropical. 
Staurastrum Meyen. 
S. orBiculare Ealfs var. JRalfisii W. & G. S. West. Loc. G, 9. 
Distr. General, except Africa. 
S. Wildemanni Gutw. Loc. 27. Distr. Eur., Tropical Asia. 
S. corniculatum Lund. Loc. 32. Distr. Europe. 
S. tauphorum W. & G. S. West. Loc. 27. Distr. Ceylon. 
S. submanfeldtii W. & G. S. West. Loc. G, 9, 10, 18. Distr. 
Ce} r lon, Central Africa. 
S. acanthastrum W. & G. S. West. Not common except in 
Tank Borlasgama and at Kekunadure. There appears to be little 
variation in details of structure, but the number of horns varies, 
sometimes being 3 or 4, and often 5 on each semi-cell. The horns of 
the respective semi-cells alternate in position. Loc. 1, 11, 32, 53, 5G. 
Distr. Ce}don. 
S. gemelliparum Nordst. Loc. 6 and 9 (rare). Distr. S. Ainer., 
India (inch Ceylon). 
S. muticum Breb. Loc. 6, 9. Distr. General. 
S. Ereemanni W. & G. S. West. Loc. 5G. Distr. Ceylon. 
G ymno z y ga E h re n b. 
G. moniliformis Ehrenb. W. & G. S. West (loc. cit.) observed 
a variety gracilescens Nordst. Our specimens agreed with the type 
(25-30 fi in length, 17*5-22‘5 g in breadth). Loc. 27. Distr. Eur., 
S. Amer., Ceylon. 
