156 
Transactions of the Society. 
Since the above species was published, we have met with zygo- 
spores of G. confusum var. reyularius ; they are very different from 
those of the above. 
21. C. confusum Cooke (Brit. Desm., p. 110). 
Yar. regularius Nordst. (Freshw. Alg. of N. Zeal, and 
Austr., p. 47, tab. v. fig. 6). PI. IY. fig. 41. 
Zygosporae globosae vel subglobosae, nodulosae, mem- 
brana externa incrassata ad nodulos. 
Diam. zygosp. 52*5-61 fi. 
Hah. Thursley Common, Surrey. 
Genus Xanthidium Ehrnb. ; Balfs. 
22. X. antilopjeum (Bre'b.) Kutz. (Cooke, Brit. Desm., p. 132, 
tab. 46, fig. 2). 
A mature zygospore of a small form of this (from Ballynahinch, 
Co. Galway, Ireland), with perfectly straight spines to the semicells, 
is figured (PI. IY. fig. 42), diam. s. spin. 45 //,, c. spin. 80 /i; a 
zygospore of a large form (from Thursley Common, Surrey), the semi- 
cells having curved spines, was also seen. The two zygospores were 
practically alike in form, the spines being furcate with the divisions 
recurved. 
23. X. Smithii Arch. var. variabile Nordst. (Freshw. Alg. of 
New Zeal, and Austr., p. 44, tab. iv. f. 27-29). PI. IY. 
fig. 40. 
Zygosporae globosae, spinis validis, brevibus, numerosis, 
apicibus leviter bifidis trifidisve vestitae. 
Diam. zygosp. s. spin. 29-31 /*, c. spin. 42-45 /*. 
Hah. Devil’s Jumps, Frensham Common, Surrey. 
The poles of the vertical view are described and figured by 
Nordstedt in his New Zealand specimens as truncate. We have 
observed this variety of X. Smithii in abundance from many localities 
in W. Ireland and the S. of England, and the majority of the speci- 
mens had the poles rounded and not truncate. 
24. X. Bobinsonianum Arch. (Quart. Journ. Micr. Sci., 1880, 
p. 114; Cooke, Brit. Desm., p. 134). PI. III. figs. 21, 22. 
This has been rather too briefly described by Archer ( l.c .) ; and as 
his promised detailed description has never appeared, there is some 
doubt as to the correct identification of our plant. However, from 
some remarks by Dr. Nordstedt in his Freshw. Alg. of New Zeal, and 
Austr., 1888, p. 44, it would appear that it is of the same species as 
that observed by Archer in Ireland. The following is a description 
of the plant seen by us : 
• X. parvum, tarn latum quam longum, profunde constrictum, 
sinu valde aperto et acutangulo sed ad extremum obtuso ; 
semicellulae transverse subrectangn lares, marginibus inferioribus 
