DUBLIN UNIVERSITY ZOOLOGICAL AND BOTANICAL ASSOCIATION. 253 
expect, perhaps, Aptogonum desmidium, /3, which, however, is distin¬ 
guished by the foramina between the joints. This view I would, then, 
very submissively put forward. In any case I do not see I have an alter¬ 
native hut to describe this form as a Sphserozosma, as follows:— 
Sphcerozosma pulchellum ( nov . spi). 
Filament very minute and fragile; joints (including inflations) 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 corpuscle. 
Length of joint, Ws-o in.; diameter of joint at the end, v§Vo ; diameter 
at widest part of inflation, vsVe in. 
I have also to bring to notice a species of Staurastrum, which, though 
minute, and not very striking in appearance, there can be no doubt is 
an undescribed one. In the front view this little organism might pos¬ 
sibly be taken for a small form of Arthrodesmus incus (Figs. 8, 10); but 
the central constriction 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 segments often seen in Arthro - 
desmus incus present in the form in question; however, an end view, 
showing its four, or frequently three angles, dispels all doubt, and at 
once proclaims the plant a Staurastrum (Figs. 9, 11). It differs from 
Staurastrum dejectum (Breh .) by its much smaller size and less deep con¬ 
striction, and angles not inflated in the end view; from Staurastrum 
cuspidatum {Breh.), the end view of which the triangular variety most 
approaches, by its much smaller size, straight sides in end view, and non- 
inflated angles, and by the want of a connecting band in the front view. 
It resembles more nearly Staurastrum minus {Kiitz.), an end view of 
which is figured in Half's’ monograph, but which has not yet (I believe) 
been found in Britain; but that species presents five angles, not three or 
four, as in this species. I do not think I need contrast it with any other 
species. The angles in the end view of the quadrangular form are right 
angles, and the .sides straight; in the triangular form the end view is 
equilateral and straight-sided, both forms possessing a single awn or 
acute spine at each angle. The awns are a little longer in the triangular 
variety than those of the quadrangular. I was fortunate enough to meet 
with the sporangium of this species (Fig. 13); it is spherical and acutely 
spinous, in fact, very like that of Arthrodesmus incus. That this form 
is a sort of connecting link, as it were, between Arthrodesmus and Stau¬ 
rastrum seems probable, from the not remote likeness in the front view 
to Arth. incus, as well as from the similarity of the sporangium in each. 
I would, therefore, venture to put forward the following to serve as a 
description of this species :— 
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