Professor Huxley's communication, relative to the discovery of a new Reptile in the Lower Chalk of the south of England, which he has called Acanthopholis horridus, may be rendered more interesting by a detailed description of its stratigraphical position and its associated organic remains, a matter of some importance in this cases, as few, if any, higher reptilian remains have occurred in the Lower Chalk of either Europe or England; whereas in the Wealden group below the Cretaceous rocks, and still lower, in the Oolites and Lias, many genera occur. The discovery by the Rev. W. Fox of a remarkable and allied reptile in 1866, from the Wealden beds of the Isle of Wight, named Polacanthus by Professor Owen, increases still more the interest of this new genus, and is another reason why it is well to understand its geological horizon.