After pointing out that the observations of Alessandrini, Rosenthal, Eschricht, and Barkow on the placentation of the seals had been limited to the determination of the form of the placenta, and to the more salient facts connected with the arrangement of the fœtal membranes, the author in this memoir proceeded to describe systematically the gravid uterus, the form and structure of the placenta, and the arrangement of the fœtal membranes of the grey seal, Halichœrus gryphus. He was indebted to Dr M'Bain and Captain Macdonald of the cruiser “Vigilant” for the opportunity of acquiring the gravid uterus of a recently killed specimen of this seal. The distribution of the utricular glands was described. The affinities between the placentation of the seals and the proper carnivora, more especially the common bitch, were pointed out.