sometimes distinct grooves, then flattening out; they are, no doubt, artificial due to pressure and partial fracture. The bone is slightly curved lengthwise, the convex surface being the grooved surface. The other or ventral is feebly concave. The third side of the tri|angular section is “mesial” where it abutted upon the “mesorostral gutter.” One margin is nearly straight. This I take to be the mesial margin where it met perhaps the nasal bone; the other irregular, being chipped at intervals. Dimension of premaxilla (cms.). Length, mesial edge 38 Width, greatest 11.5 Width at each end 9 Thickness, greatest 5 Thickness, outer edge 1.5 As to the interpretation of this bone the apparent hollowness: the matrix enveloped in this layer of bone, led me to think at first that it was part of a mandible, but there is no trace of teeth or sockets, and in Zeuglodonts the teeth extend the whole length of the jaw bone. But the grooving on the one surface makes it more likely to be a bone from the upper surface of the skull, so it may be either a nasal or premaxilla. It does not fit against the end of either of the two crania, and it was found at a different date and time, though it comes from Milburn. Comparing it with Prozeuglodon atrox, with skull of 60 cm. length, the premaxilla is 27 cm. and the nasal 16.5 cm., and as the measurements of the skull of Lophocephalus indicate a longer skull there is no incompatibility in regarding this bone as a pre|maxilla. Mandible. There is no record as to the provenance of this, but the matrix resembles the Clarendon rock in which teeth occur (p. 6). This mandible has the condyle entire, but the coronoid is lacking, though it seems to be concealed in the matrix, for the edge of the bone is traceable into this. There is no sign of teeth nor of alveoli, so presumably much of the anterior region is missing. The outer face has a rounded ridge along its middle starting from a slight but distinct knob just in front of the rounded condyle. The bone rests upon the rock so that its inner face is not visible, but on another mandible which is free this face is smooth. The upper and lower margins are entire except for a short distance along the latter edge.