Sir R.I. Murchison placed in my hands a few days ago seven photographs, three of which are stereoscopic, of , perhaps, the most extraordinary mammalian fossil yet discovered in Australia. These photographs, with a brief printed notice of their subject by Wm. Sharpe Macleay, Esq., F.R.S., and some MS. notes by J.D. Macdonald, M.D., R.N., had been transmitted to Sir Roderick by his Excellency the Governor Sir W. Denison, from Sydney, New South Wales ; and it is by the desire of Sir Roderick Murchison that I now bring the subject under the notice of the Geological Society of London, to whom Sir Roderick desires to present the Photographs, on the part of His Excellency, Sir Wm. Denison. I had, some weeks previously, received from my friend and correspondent, George Bennette, Esq., F.L.S., of Sydney, New south wales accompanying outlines of the same fossil skull, made by him on the reception of the specimen by the authorities of the Australian Museum at Sydney, and I had penned notes of my comparisons of this sketches before receiving the photographs and descritions of the fossil skull from Sir Roderick I. Muschison. Mr. Macleay's description appears in a Report on "Donations to the Australian Museum during August, 1857," published in a Sydney newspaper of about the same date. It is as follows:— “Fossil Skull of a new marsupial animal, which bears a nearer approach to Diprotodon than to any other known genus. The size was apparently that of a large ox; and the