136 PROCEEDINGS OF SOCIETIES. 
being wider at the basal inflation of the segments than at 
the ends, not, as in Spherozosma excavatum, with rounded 
ends wider there than at the centre, and having a deep, wide 
sinus at both sides of the jomt. I may add that, so far as 
my humble experience goes, the “junction-glands” of 
Spherozosma excavatum are often very obscure. The sepa- 
rated jomts of the form of which I have tried to convey 
a conception, closely resemble a minute form of Cos- 
marium, and such I thought a single joint was till I met it 
in lengthened filaments. 'To obviate the difficulty here met 
with, two courses may appear to be open: either to allow 
this plant to remain as an aberrant member of the genus 
Sphzrozosma—an unadvisable course if it could be avoided 
—or else to alter the characters of the genus by omitting the 
“junction-glands” as essential to it, for it appears, I think, 
that the plane or compressed filament is itself enough to 
distinguish Sphzrozosma from the cylindrical or angular 
filamentous genera, except, perhaps, Aptogonum desmidium, 
/, which, however, is distinguished by the foramina between 
the joints. This view I would, then, very submissively put 
forward. In any ease Ido not see I have an alternative but 
to describe this form as a Spherozosma, as follows :— 
Spherozosma pulchellum, n. sp. 
Filament very minute and fragile; joints (including infla- 
tions) about as broad as long; ends truncate, with square 
angles; segments suddenly inflated at the base, and separated 
from each other by a shallow acute notch, thus giving to the 
margin, at each side, a pouting appearance at the central 
constriction, each segment of the joints containing a single 
central light-coloured fs SL) 
Lea of joint, z5'55 n.; diameter of fea at the end, 
assy 3 diameter at widest part of inflation, zasp IM. 
I have also to bring to notice a species of Stawrastrum, 
which, though minute, and not very striking in appear- 
ance, there can be no doubt is undescribed. In the front 
view this little organism might possibly be taken for a 
small form of Arthrodesmus incus; but the central con- 
striction is not so deep, nor is the constricted portion so 
narrow, nor are the segments comparatively so dilated at the 
ends, nor is the gibbous appearance at the base of the seg- 
ments often seen in Arthrodesmus incus present in the form 
in question; however, an end view, showing its four, or 
frequently three angles, dispels all doubt, and at once pro- 
claims the plant a Staurastrum. It differs from Stau- 
rastrum dejectum (Bréb.) by its much smaller size and 
