NEW OR CRITICAL BRlTTStt aLGA5. 
‘22 
Mixed with various other species of perforating algse in old 
shells from Cumbrae. I am indebted to the kindness of Dr. 
Bornet for the identification of this species. I find that the plant 
is far from uncommon on our shores, as I have also found it 
abundantly on old shells from Weymouth and elsewhere ; exter- 
nally the shells give no indication of the presence of the Plecio - 
nema t which is only brought to light when the chalk of the shell 
has been dissolved. 
Symploca atlantica, Gomont , Monographic des Oscillariees, Ann. Sc. 
Nat. Bot., t. xvi., p. 109. 
Csespitose, black green. Fasciculi erect, reaching one centi- 
metre high. Filaments closely interwoven, free, simple, strongly 
and angularly torulose. Sheaths thin, firm, turning blue when 
treated with chlorzinc iodine. Trichomata yellowish-green, 
4-6 /JL thick, constricted at the joints throughout their entire 
length, cells usually square or shorter than long, rarely longer 
than broad, 2-6 p long, protoplasm scarcely granulose ; dissepi- 
ments visible, pellucid, not granular ; membrane of the apical cell 
thickened into a depresso-conical calyptra (n.v.) 
Hab. Shores of Wales (Nordstedt). 
The above description is translated from M. Gomont’s descrip- 
tion of the species. I have not had an opportunity of seeing a 
specimen, and record the species as British, on the authority of 
M. Gomont, who has received specimens gathered on the shores of 
Wales by Dr. Nordstedt. We are not told the exact locality in 
Wales where the plant was found. 
Lyngbya lutea, Gomont , J Essai de classijication des Nastocacees 
homocystees in Morot, Journal de JSotanique , iv., p. 354. 
Stratum sub-gelatinous, coriaceous, yellowish-brown or olive- 
green, when dry often blackish violet. Filaments twisted, flexuous, 
closely interwoven. Sheaths hyaline, smooth, turning blue when 
treated with chlorzinc iodine, at first thin, when old up to 3 p in 
thickness and lamellose. Trichomata olive-green, not constricted 
at the joints nor attenuated at the apices, 2 ‘5-6 p thick ; cells 
quadrate or up to three times shorter than long, 1*5 p to 5*5 p 
long, protoplasm granular, dissepiments usually compactly drawn 
together. Apical cell furnished with a rounded calyptra. 
In shallow puddles of salt water at high-water mark, Puffin 
Island and Cumbrae. This species greatly resembhs Lyngbya 
semiplena in outward appearance, but, as M. Gomont remarks, is 
sharply separated from it by the smaller diameter of the filaments, 
the greater length of the joints, and the reaction of the sheath in 
the presence of iodine. 
Phormidium fragile, Gomont , Monographe des Oscillariees , l.c.,p, 163. 
Stratum slimy, lamellose, yellowish or brownish-green. Sheaths 
dissolving to a fibrous, gelatinous mucus, which does not turn 
blue when treated with chlorzinc iodine. Trichomata more or 
