272 ALG& ANTARCTICA. 
culis ramorum diametro sesqui-subduplo longioribus, ra- 
mulorum diametrum subequantibus. 
Has. Christmas Harbour, Kerguelen's Land, rare. 
Fronds 2-5 inches long, slender, rather rigid, much and 
distichously branched ; all the branches jointed, and of equal 
breadth throughout. Ramuli 4 line long, issuing in opposite 
pairs from the middle of every joint throughout the length 
of the frond, pectinated on their upper face with secondary 
ramuli, thick, subacute, and very patent. Colour brownish 
red. This so closely resembles C. Plumula, that it is diffi- 
cult by mere words to discriminate them; yet on comparing 
them together on the table of the microscope, they are ob- 
viously not the same. Our C. simile is a much coarser, 
more rigid plant; its ramuli are more robust in proportion to 
the diameter of the joint, and the joints are shorter. We are 
the more disposed to keep it specifically distinct from C. Plu- 
mula, with which we were at first inclined to unite it, because . 
specimens clearly referable to that species were found at 
Cape Horn; so that the differences above noticed do not 
appear to originate in difference of local circumstances. 
54. Callithamnion Ptilota, nobis ; fronde (parvula) rigida se- 
. tacea pinnatim ramosissima, ramis vix distichis venoso-stri- 
atis subopacis, secundariis opposite pinnulatis, pinnulis 
simplicibus patentibus subulatis e quoque ramorum gent- 
culo ortis, articulis diametro duplo longioribus. 
Has. Off the Crozets, on Macrocystis pyrifera. 
Frond 1-2 inches high, solitary, as thick as a hog's bristle, 
much branched in a pinnate manner, but not strictly dis- 
tichous. Secondary branches closely pinnate. Pinnule 
opposite, subulate, simple, issuing from every joint. Colour 
brownish-red. Substance rigid and scarcely adhering t9 
paper. Only a single specimen of this very distinct species 
was met with. 
55. Callithamnion ¢ernifolium, nobis ; pusillum vage dichoto- 
mum, ramis pellucide articulatis, ramulis sæpissime ternis 
e quoque ramorum geniculo enatis brevibus tenuibus sim- 
