Order Archaeoceti Family Zeuglodontidae Lophocephalus parki n.gen. et n.sp. The length of the larger cranium is 46 centimetres from posterior edge of occipital condyle to extreme end, that of the smaller 32.5 cm. Each is broken across anteriorly at approximately the same place, viz., at a short distance behind the junction of parietal with frontal bones. As the larger cranium has the occipital region more complete than the smaller one, I take it as the type of the genus, though the smaller one has a greater relative length of parietal bone remaining, being broken across slightly nearer to the frontal. The supra-occipital slopes upward and forward from the foramen magnum forming a large triangular shield as in Prosqualodon; it is slightly concave from side to side; its lateral margins where it meets the exoccipitals and parietals rise up so as to produce a fairly well-defined lambdoidal crest to which the hinder margins of the parietals contribute; these two ridges or crests meet anteriorly in the middle line and coalesce with the sagittal crest. In the smaller skull the shield is incomplete posteriorly, and the lambdoidal crest is also broken laterally. The length of the supra-occipital shield is 26 cm., its breadth 18 cm. The inclination of this bone is greater than that figured for those species of which the literature is available to me, viz., Zeuglodon osiris and Prozeuglodon atrox of Andrews, where, indeed, the bone is nearly vertical, so that I suspect that in the present crania there must have been a downward compression or crushing previous to fossilisation; but both of them exhibit the same slope. The exoccipital region is fairly well preserved in the larger skull; the left condyle is entire, the right one broken away; the breadth over the two condyles would be 16 cm.; the width of the condyle is 6.5, its height 8 cm. The foramen magnum has a height of 4 cm. and a width of 7 cm. The parietal bone is of considerable extent; indeed, it is relatively enormous as compared with the bone in existing Odontocetes and in the Squalodonts. Unfortunately the lower margin is broken away and the squamosal has also gone. A portion of the parietal has also been torn away above the region of the squamosal so that the “brain” is exposed. At the extreme anterior region of the bone there are a few short longitudinal cracks, indicative of some degree of pressure. In Prozeuglodon and other members of the family the cranium is much constricted in the anterior region of the parietals; but in the present specimen there is not sufficient of the cranium to show this. In the smaller cranium in which relatively and absolutely a greater length of this bone is preserved, the former of these injuries is absent. In this smaller cranium the length of the bone on the right side along the ventral broken margin is 26 cm. measured from its junction with the exoccipital; its height from the top of the sagittal crest to this lower margin is 13.5 cm. along the surface of the bone. The roof of the cranium is at the anterior end very thick,