In this paper an anatomical peculiarity was described which is occasionally found both in Man and the Cetacea. It is not due to a bifurcation of the shaft of a single rib at its vertebral end into two heads, but to the fusion of what ought to have been the shafts of two distinct ribs into a common body, and it invariably occurs at the apex of the thorax. Although the author had long been familiar with dried specimens from the human body in the Anatomical Museum of the University of Edinburgh, two cases which he now describes were the first that he had seen in the subject itself in the course of nearly thirty years' experience as a teacher of anatomy, and it is remarkable that they should both have occurred within a few months of each other. A third specimen occurred in a skeleton in the possession of one of his pupils, Mr Minas S. P. Aganoor.