306 
Proceedings of the Royal Irish Academy. 
But, nevertheless, all the four forms are, I venture to suppose, suffi- 
ciently clearly to be regarded as closely kindred — they are all com- 
pressed, angular, deeplj^ subdivided either by narrow, even linear inci- 
sions, or by broad, angular, or rounded sinuses. 
The third form referred to (figs. 11, 12), with itstwobroadly-cuneate 
segments is comparable to T. Crux-Michaeli, as it were, deprived of two 
opposite segments ; no doubt, even for a moment supposing it possible 
to operate on an example so as actually to remove two of its segments, the 
result would still not be at all identical with my form in the contour of the 
remaining segments ; therefore, so far as one can fairly judge, it would not 
be a reasonable assumption to regard it as a binate or, so to say, depau- 
perated variety of T. Crux-Michaeli (Reinsch). It does seem the new form 
alluded to is not apparently at any time, so far as it has presented itself, 
divided incisuris quaternis," yet still the approximation or affinity" 
cannot but be regarded as sufficiently striking. The fourth form (figs. 14- 
16), with its three angles only, audits slender filiform or bristle-like pro- 
cesses, appears indeed more distinguished from the rest ; but apart from 
having but three apices, its more projecting but comparatively less broadly 
roanded lobes, call to mind Reinach's (unnamed) form, fig. 8, with its 
four semicircular lobes, cruciately arranged, and with a shallow subacute 
(instead of a broadly-rounded) sinus between them. As before, we 
might momentarily suppose it possible to deprive one of such forms as 
fig. 8, of one of its semicircular lobes, and the remainder " shoved round" 
so as to render the now (supposed) but three to become equidistant, still, 
even apart from the bristles, the forms would not be alike, yet, as in 
the previous case, the approximation or affinity" cannot but be re- 
garded as sufficiently striking ; and further, my fourth form, this 
admitted, would seem thus (through such as fig. 8), to be connected 
even with T. gothica (Reinsch). 
So far then as our acquaintance with these little algse here referred 
to reaches, there appear to exist four (if not five), distinct, yet kindred 
forms of figured " Chroococcacese."-— their remarkable shapes preclude 
their being regarded as Lichen-gonidia," but whether mature plants 
or stages in the growth of any more complicated structures remains a 
problem. Ours are at least forms which here and there recur, and one 
can at once recognise them as always offering the same characteristics, 
and as maintaining their apparent individuality. "Whether they are 
species" or not, it may be a matter of convenience, should observers 
meet them elsewhere, and be able to throw a light upon them, to have 
at least a means of their recognition. For the reasons mentioned, it 
occurs to me as preferable (at least provisionally and temporarily) to 
record them under Reinsch' s genus, if indeed that observer may not 
consider it unallowable so far to modify the terms thereof as to admit 
of its embracing the two new forms. It may be objected that the very 
name of the genus would preclude the admission of a fhr ee-lobed form 
into it, but the name Staurastrum is retained, though only a minority 
of the forms referrible thereto are cruciate or quadrangular in end-view ; 
so also, with Triceratium — where four and five-angled forms occur, 
