PROCEEDINGS OB SOCIETIES, 67 
quite so divergent as in the figure in Ralfs, but there could not 
be a doubt but that the present plant was the same species.— 
Another rare form was Stawrastrum oligacanthwm (Bréb. in herb.) ; 
this, however, Mr. Archer had once gathered here before. The 
present specimens came from the same pool as St. pungens. 
Staurastrum oligacanthum is an unpublished species of M. de 
Brebisson’s ; that skilled algologist had sent specimens and draw- 
ings thereof to Mr. Archer a couple of years ago. Of the identity 
of the present plant with the French specimens there could be no 
doubt, nor of the species being in itself exceedingly well marked 
and quite distinct. He supposed it would be presently figured 
and described.—Another rare species exhibited by Mr. Archer 
was one he was inclined to regard as Stawrastrum (Phycastrum) 
Griffithsianum (Nig.); of this form he, of course, had never seen 
authentic examples, and he had long been disposed to regard Phy- 
castrum Griffitheianwnm (Nag.) (‘Gattungen einzelliger Algen,’ 
p. 128) as identical with Stawrastrum spongiosum (Bréb.). But 
Staurastrum spongiosum (Bréb.) occurs, too, as a somewhat great 
rarity near Dublin, and, comparing the present plant therewith, 
especially in the end view (best seen in an empty frond), it seems 
to agree much better with Nageli’s figure (op. cit. t. viii, c. 2). 
In St. spongiosum the end view shows the sides convex, the spines 
evenly distributed, whilst in S¢. Griffithsianwm there is a some- 
what deeply rounded concavity, destitute of spines at the middle, 
on each side. These two seem, therefore, distinct. Their rarity, 
however, prevents a due examination and comparison.— Mr. Archer 
also showed specimens of Closteriwm prelongum (Bréb.), this 
being, so far as recorded, the second time it had occurred in this 
country. On the first occasion it was met by Mr. Dixon in a 
stream running into the Grand Canal near the city, mixed amongst 
attached filamentous alge (Bangia atropurpurea and Ulothrix 
zonata), but exceedingly sparingly. The present specimens 
occurred amongst Spirogyre and other Closteria in a ditch close 
beside the Royal Canal, also near the city. The examples now 
found were not quite so long as those which presented themselves 
on the first occasion, nor as De Brébisson’s figure (‘ Liste des 
Desmidiées observées en Basse-Normandie,’ t. ii, 41), but this 
notwithstanding they both represented one and the same species, 
one exceedingly elegant and well characterised. 
Mr. Archer likewise laid on the table fine examples of Coleo- 
chete scutata in all stages of growth, from young plants of two 
cells up to the largest discs, the latter showing the oogonia fully 
developed. 
July 20th, 1865. 
Mr. Archer showed a large (Edogonium, which he felt inclined 
to regard as exceedingly closely related to, if not identical with, 
Vaupell’s Gdogonium setigerum, described in his ‘Iagttagelser 
