A lthough the carnivorous Dinosaur Megalosaurus was first discovered in the Stonesfield Slate nearly 80 years ago, and is now represented by numerous fossils from the Bathonian and later Mesozoic formations of England, its skull has hitherto been known only by unsatisfactory fragments of jaws. Our acquaintance with the Megalosaurian type of skull has depended solely on discoveries of nearly complete specimens in the Jurassic and Cretaceous formations of North America. At last, however, Mr. F. Lewis Bradley, F.G.S., has been able to submit to the Society the greater part of a skull obtained some time ago from the Great Oolite in an excavation for a reservoir at Minchinhampton (Gloucestershire); and he has prepared the specimen with so much skill and success that it is beautifully exposed for study from the left side (Pl. XIII, fig. 1). It is rather small, measuring only 26 centimetres in total length, but there cannot be much doubt that it belongs to the genus Megallosaurus itself. The upper portion of the fossil is unfortunately destroyed by an irregular fissure in the rock, which is partly filled with calcite. The cranium is, therefore, scarcely seen; but there are traces behind of the occiput, which is somewhat deeper than wide above the foramen magnum, and lies in a plane inclined much forwards. The external bones of the temporal region and face are remarkably thin and delicate, and in their crushed condition it is difficult to distinguish the sutures between them. The large vacuities, however, which form so