The object of the present communication is to briefly consider the general and minute structure of the corallum of the recent Tubipora musica, with special reference to the association of the genus Tubipora with the extinct genus Syringopora, as advocated by many modern naturalists. The method of inquiry that I have pursued in carrying out this investigation has been principally that of preparing similar thin and transparent sections of both the recent and the extinct types; and though there are special difficulties in the way of any examination of Tubipora by this method, I have been able to overcome these in a satisfactory manner, and to prepare a number of thin sections which answer all the requirements of the case.