ABSTRACT The western coast of Ireland has always been regarded as good collecting ground by the naturalist ; and yet, so far as its marine fauna-is concerned, it may be said to be altogether unexplored. This is true, not only of its invertebrate, but even of its vertebrate animals; and any young ardent zoo legist will still find plenty of work to do among the western Phocidæ and Fish, and almost a new field in the shell-less Molluscs, Annelids, and Coelenterata, of Donegal, Sligo, Mayo, Clare, and Kerry. At one time, I had hoped to have been able to investigate the mafine fauna of western Cork and Kerry, making Bearhaven and Ventry my headquarters; but since my report on this subject to the British Association in 1857 professional engagements have prevented me from devoting the requisite time to this pursuit. I have, however, in the course of this spring, received, by the kindness of W. Harte, Esq., C.E., County Surveyor for the northern district of Donegal, several small collections of marine animals from Rathmullen, in that county; and as these all for the most part bore easily the carriage by night to Dublin, I have been able—reviving them with the help of several large aquaria ——to add some new species to the Irish fauna. With care, I have thus received in perfect health such delicate creatures as Pectinaria Bélgica, Eolis alia and Drummondi, Siphonostoma undnata, Hydra tuba, and others ; but none of them more interesting than the little solitary Alcyonarian Actinoióón which it is the Object of this paper briefly to describe.