204 NEW SPECIES OF RHODOCHORTON. 
RHODOCHORTON SEIRIOLANUM, Sp. nov. 
Diagnosis. Thallus filamentis rectis, eramosis, e strato eellularum 
surgentibus; tetrasporangia vel terminalibus vel secundis, 
vel utrisque ; colore roseo. 
Hab. On Polysiphonia urceolata at low water, Puffin Island, 
Anglesea. 
On examining some old Zaminaria-stems gathered at extreme 
low water (spring-tide) at Puffin Island (S. Seiriol's Isle), Angle- 
sea, in March 1890, I found some epiphytic Polysiphonia 
urceolata covered with the minute species which I here describe. 
I submitted specimens to Mr. G. Murray, F.L.S., who believed 
it to be a new species. I sent specimens also to M. Bornet, 
who was kind enough to give me his opinion on the matter. 
I had considered it as a species of Rhodochorton, but M. Bornet 
pointed out to me that the discoid basal layer indicated affinity 
with Chantransia. Its general appearance and the presence of 
well developed and abundant tetraspores, however, clearly 
demonstrated an even closer relation to the genera Rhodochorton 
and Callithamnion. Indeed, M. Bornet suggested the possibility of 
its being near Callithamnion humile, Kiitz., in systematic position. 
In that species, however, the apices of the upright filaments, at 
least in Kiitzing’s figure, are branched, while in my plant the 
filaments are quite simple. In character it seems halfway 
between the genera Rhodochorton and Chantransia, but I insert 
it temporarily under the former and venture to give it the name 
of Rh. seiriolanum, after the island on whose shores I found it. 
Whether it may be left there, or form the type of a new 
genus, or whether, as suggested to me by Mr. Batters, the 
genus Rhodochorton must be divided into two subgenera, one 
with a discoid base, the other with creeping filaments, I leave 
for discussion in a paper on the revision of the genus Rhodo- 
chorton on which I am engaged. 
I may add that I have found in the present species the same 
mode of innovation of sporangia I have described above for 
R. Rothii, R. floridulum, and R. membranaceum. 
EXPLANATION OF PLATE XXXIV. 
Figs. 1-5. Rhodochorton seiriolanum, n. sp. 
Fig. 1. Part of a branch of Polysiphonia urceolata with R. seiriolanum epiphytic 
on it, x 55. 
