NOTICES OF BOOKs. 93 
view equally elliptic, aii with long spines cleft at summit—and 
Cosmarium margaritiferum (Turp. )—segme ments semiorbicular, upper 
margins somewhat truncate, in end-view elliptic, somewhat prominent 
at the middle at each ae the central pearly mite being the largest, 
zygospores covered by not very numerous, rather large, and pellucid 
hemispherical cahomtek hs Cosmarium quinarium, Lundell [occurs in 
Ireland, very eo C. caesar Lund., C. mtr sss Lund. 
sum, Nag., as the author mentions]; Stawrastrum aversum, Lun- 
dell [occurs in Toslont; rarely, and appears doubtless a good species] ; 
Staurastrum O’ Mearti, Arch. [the author thinks this to be a triangular 
form of Arthrodesmus ‘Incus, B. intermedius, Wittrock. In this he has 
but anticipated our own view, that Wittrock’s is a compressed or 
plane form of S. O’Mearii, Arch., and not seemingly a variety of 
All 
A. Ineus at all. these occur in Ir eland. Several typically tri- or 
multi- angular species of Stawrastrum of different types are known to 
possess their two-angled or two-rayed ; Staurastr 
and S, 
Treland ; the latter is an especially elegant form, and one extremely | 
hard to be believed to be but a mere varietal form of the former. Of the 
latter species the author finds in Norway a form supernumeraria—that 
is, possessing on the upper surface 1-3 short, truncate, minutely cleft 
well-marked, and not uncommon in Irelan 3 S. pseudocrenatum, 
identical wi ith 8. Maamense, Archer, a form — met with i in the 
South and West of Ireland, also at Ambleside e, W and 
avery well-marked and constant species]; S. nase (Ehr.), Bréb. 
[the author met with an example one segment with the character of S. 
Jurcatum, the other _ that of S. Senarium (Ebr.). This is probably 
not surprising ; those two forms seem to beara relation to one another 
comparable to that of 8. _farcigerse, ness to S. pseudofurcigerum, 
insch ; ; €xamples indeed occur in on and the same gathering, with 
and witho ut the nocneset ai ae this contrast may be 
pon pa seen in the osite segments of one and the same 
‘individual ] ; ae Sa gracile, Ralfs [the malls meets with 
a two-rayed form—f. bicorne, Bulnheini+which occurs as yet in 
