ON ACTINOTHRIX. 887 
magni, flavo-brunnei, leves. Calyptra magna, leptoderma, albido- 
straminea, apice brunnea, a filis paraphysimorphis flavis, flexuosis, ser- 
ratis a pluribus seriebus cellularum incrassatarum formatis, vestita.— 
Inflorescentiam masculam invenire mihi non contigit. 
Stockholm, 15 Julii, 1864. [Received by us Nov. 12.—Ep.] 
ON ACTINOTHRIX, A NEW GENUS OF OSCILLATO- 
RIACEA, FROM THE COAST OF IRELAND. 
By Dr. J. E. Gray, F.R.S.- 
My daughter, Mrs. Stokes, when on a visit in Ireland last autumn, 
seht to her mother a few specimens of Alge, which she picked up on 
the shores of Dingle Bay, merely for the purpose of showing the very 
bad state in which the few weeds there were at that time. On exa- 
mining them under the microscope, Mrs. Gray discovered a form which 
she did not recognize, and referred it to me for my opinion. After 
consulting various systematie works, I am induced to consider it asa 
new type of form among the Oscillatoriacee. The short internal 
joints of the filaments clearly place it in this suborder. It has also 
some alliance to the Rivularie, from the tapering form of the young 
filaments, but instead of these being united together in a solid frond, 
or tufted and stratified like the Oscillatoriacee, they diverge in a ra- 
diating manner from the whole surface of a small, central, solid mass. 
The plant was found in all states of development, intermixed with the 
filaments of a Cladophora that had been rolled into a mass on the sea- 
shore. In the young state, the central mass is large and the filaments 
very short and conical; as the plant grows they elongate and become 
more cylindrical, the central mass becoming relatively much smaller. As 
it swims about freely in the sea, it must be a beautiful object,—the young 
plants looking like minute green stars, and the older resembling very 
small medusæ or jelly-fish, with long green threads instead of arms. 
The peculiarities enumerated are so remarkable that I propose to 
establish for it the genus Actinothriz, and I must consider it as the 
type of a new tribe Actinothricinee. The genus may be thus charac- 
terized :— 
- AcrINoTHRIX.—Filament elongate, subeylindrical, rather flaccid, 
