od PALBONTOGRAPHICAL | SOCIRTY. -INSTITUTED MDCCCXLVII. LONDON: MDCCCXLIX, MONOGRAPH THE FOSSIL REPTILIA OF THE LONDON CLAY. PART I. CHELONIA. BY PROFESSOR OWEN, F.R.S. F.L.S. F.G.S. &c. AND PROFESSOR BELL, Sec.R.S. F.L.S. F.G.S. &c. LONDON: PRINTED FOR THE PALHZONTOGRAPHICAL SOCIETY. 1849. Cc. AND J. ADLARD, PRINTERS, BARTHOLOMEW CLOSE. ADVERTISEMENT. WHEN my friend Professor BrLu consented to the announcement, by the PALEONTOGRAPHICAL SOCIETY, of a Monograph by himself on Fossil Reptiles of the London Clay, he was not aware of the progress already made in my work on the Fossil British Reptiles. As soon as he saw the proofs of the plates of those from the London Clay he renounced his intention; but, on the completion of the arrangement with the Council of the Society for the publication of my work, he kindly consented to allow his name to be associated with mine in the present Monograph, to which he has contributed a very valuable and important share. The aid, however, which Professor Bell has rendered has not ended with the descriptions which bear his initials. By his careful revisions of those contributed by myself their accuracy has been assured; and I should not have dismissed the sheets containing the determinations of the parts of the complex skeleton of the Chelonia, and the nomenclature applied to them, with the confidence which I now feel, if they had not received the sanction of an anatomist and naturalist who had distinguished himself in a comparatively early part of his scientific career, by his beautiful Monograph on the existing species of the Chelonian order of Reptiles. It only remains to add, that we have mutually co-operated in ensuring the accuracy of the illustrations, and have been most ably seconded by the experienced artists Messrs. Dinkel and Erxleben, to whom we beg to offer our best thanks. Our acknowledgments to the kind friends who have liberally submitted their specimens of Eocene Chelonia to our examination are expressed in the text, in which those specimens are respectively described. Ry, Os Digitized by the Internet Archive in 2011 http://archive.org/details/monographof211 849pala _ al CONTENTS. OrRDER—CHELONIA. Family—Marina. Genus—CHELONE Species — breviceps — longiceps — latiscutata — convexa — subcristata — planimentum — crassicostata . — declivis — trigoniceps — _euneiceps — subcarinata Supplemental remarks on the species from Harwich Summary on the genus Chelone Family—fluvialia. Genus—TRIONYX Species — Henrici — Barbare — iierageatus — marginatus — TIVOSUS — planus — circumsulcatus = pustulatus 25 Vill CONTENTS. Family—Paludin Osa. Genus—PLATEMYS Species — Bullocki — Bowerbankii Genus—Emys .- Species — testudiniformis — levis -— Comptoni — bicarinata — Delabechi — crassus PAGE ~ Lis? 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Coll., Cambridge. Fraser, William, Esq. Drainage Office, Borris in Ossory, Queen’s County. Fryer, Alfred, Esq. Ventnor, Isle of Wight. Fryer, J. H. Esq. Whitley House, North Shields. Fuge, J. H. Esq. F.R.C.S.E. Plymouth. Fuller, Henry J., M.D., 45, Half Moon-st. Gabb, D. H. Esq. 5, Wellington-square, Hastings. Galton, Douglas, Esq. R. E. 20, Duke-street, St. James’s. Gandy, Gerard, Esq. Kendal. Gassiot, I. P. Esq. F.R.S. &c. Clapham. Gavey, George KE. Esq. Chipping Camden, Gloucestershire. Geological Society of Manchester. Gibbs, John, Esq. Evesham. Gibbs, John, Esq. Norville House, Evesham. Gibbs, John, Esq. Birmingham. Gibson, G. S. Esq. Saffron Walden. Gillett, J. A. Esq. Bank, Banbury. Glossop, F. H. N. Esq. Isleworth. Godlee, Rickman, Esq. 4, Queen-square. Gomonde, W. H. Esq. 26, Promenade, Chel- tenham. Gordon, P. L. Esq. Craigmyle. Gough, Thomas, Esq. Kendal. Gough, Capt. the Hon. G.S., F.L.S. &c. 24, Upper Brook-street, Grosvenor-square. ~ Gould, John, Esq. F.R.S., L.S., Z.S. &c. Broad-street, Golden-square. Gourlie, William, Esq. 8, South Frederick- street, Glasgow. Gower, A. Lewis, Esq. F.G.S. &c. 31, Finsbury-square. Graham, Thomas, Esq. M.A.,F.R.S., G.S.&c. Prof. of Chem. Univ. Coll. London, 9, Tor- rington-square. Gratton, Joseph, Esq. 94, Shoreditch. Gray, I. E. Esq. F.R.S., G.S. &c. British Museum. Gray, W. Esq. F.G.S. &c. York. Gray, C. Esq. Bilston. Gray, John, Esq. New-street, Dudley. Greenough, G. B. Esq. F.R.S., G.S. Grove House, Regent’s-park. Griffith, R. Esq. F.G.S. &c. Dublin. Grundy, Thomas, Esq. Northampton. Guest, Sir J. J. Bart. F.R.S., GS. &c. 8, Spring-gardens. Guise, W. V. Esq. F.G.S. &c. Elmore-court, near Gloucester. Guthree, M. G. Esq. 19, Saville-row. Gwilt, George, Esq. Union-street, South- wark. Haines, C. Y., M.D. 26, Warren-place, Cork. Hall, Charles, Esq. Ansty. Hall, Henry, Esq. Alton, Hants. Hall Library, Albany, New York, U.S. Hall, Robert, Esq. 8, Dean’s-yard, West- minster. Hall, William, Esq. Feversham, Kent. Halle, University, Library of Hambrough, B. J. Esq. F.G.S. &c. Niton, Isle of Wight. Hamilton, E. M.D., F.L.S. 22, Grafton- street, Bond-street. Hamilton,W. J. Esq. M.P. Sec.G.S.Chesham- place, Pimlico. Harbin, Rev. Chas., M.A. Hindon, Wiltshire. Harmar, Richard, Esq. 9, Park-street, Bath. Harris, J. H. Esq. Deddington. Harris, W. Esq. Charing, Kent. Harrison, Dr. W. Hume-street, Dublin. Harvey, Alexander, Esq. 4,South Wellington- place, Glasgow. Harvey, W. H., M.D., Trinity College, Dublin. Hastie, Honorable Alexander, Lord Provost of Glasgow. Hastie, James, Esq. F.G.S. &c. Grove-hill- terrace, Camberwell. Hastings, The Marchioness of, Efford House, Lymington, Hants. Hawkes, Rev. Henry, B.A., F.L.S. &c. Jubilee-terrace, Southsea, Portsmouth. Hawkins, M. R. Esq. 7, Russell-square. Hawley, Richard, Esq. East Leake, Not- tingham. Haworth, Thomas, M.D. Bolton. Haycock, William, Esq. King-street, Hud- dersfield. Head, Mrs. J. Ipswich. Heathcote, Thomas, Esq. Sidmouth. b x LIST OF MEMBERS. Heddle, Robert, Esq. Kirkwall, Orkney Islands. Henslow, Rev. Jno.S., F.L.S., G.S. &C.P.S. Prof. Bot. Camb. Hitcham, Bildeston, Suffolk. Hepworth, Rev. R. Tewkesbury. Herbert, J. M. Esq. F.G.S. &c. The Priory, Bodmin. Herbert, Thomas, Esq. Park, Nottingham. Heywood, James, Esq. F.R.S., G.S. &c. Athenzeum. Hickes, Thomas, Esq. Gloucester. Higgins, E. T. Esq. 25, Spurrier Gate, York. Hollis, W. M. Esq. Lewisham. Holmes, George B. Esq. Horsham. Holroyd, Rev. Jno. Leeds, Yorkshire. Hone, Joseph, Esq. M.R.D.S. 72, Harvest- street, Dublin, Hony, Rev. W. E., F.G.S. &c. Archdeacon of : Sarum, Baverstock, near Salisbury. Hopkins, W. Esq. M.A., F.R.S., G.S. Cam- bridge. Hooker, J. D., M.D., F.L.S. &c. Kew. Horner, Leonard, Esq. F.R.S., G.S. River- mede, Hampton Wick. Howitt, Thomas, Esq. Lancaster. Hubbard, George, Esq. Bury St. Edmunds. Hubbard, Jno. R. Esq. Leeds, Yorkshire. Hudson, Robert, Esq. F.R.S., G.S. Clapham. Hughes, Rev. J..M.A.Wombourn, Staffordsh. Hull, W. D. Esq. F.G.S. &c. Woodham, Rostrevor, Ireland, and Hatch-street, Dublin. Hunt, Z. D. Esq. F.G.S. Aylesbury. Hunter, Rev. S. Wolverhampton. Huntingdon, F. Esq. Hull. Hutchins, Miss, Alton, Hants. Hutton, R. Esq. F.G.S., M.R.LA, &c. Putney Park. Ibbetson, L. L. B. Esq. K.R.E., F.G.S. &c., Clifton House, Old Brompton. Illingworth, Rev. E. A. 18, Chester-street, Grosvenor-place. Illingworth, R. S. Esq. 6, Connaught-square. llott, J. W. Esq. Bromley, Kent. Image, Rev. Thomas, M.A., F.G.S. &c. Whepstead, near Bury. Inglis, James, M.D. &c. Halifax. Inskipp, James, Esq. Godalming. James, Captain H., R.E., F.G.S. &c. Geolo- gical Survey, Craig’s-court, Charing Cross. Jameson, John, Esq, 33, Blacket-street, Newcastle-on-Tyne. Jackson, Miss, Manor House, Lexden, near Colchester. Jackson, John, Esq. Dunstable. Jeffreys, J. G. Esq. F.R.S., L.S. Swansea. Jenkyn, Rev. T.W., D.D., F.G.S. &c. Coward College, Torrington-square. Jennings, F. M. Esq. M.R.I.A. &c. Cork. Jewsbury, F. Esq. Gloucester. Johnes, J. Esq. Dolan Cothi, Llandovery, North Wales. Johnston, Prof. J. W., F.R.S. L. and E. Durham. Johnston, Dr. George, Berwick-on-Tweed. Jones, Capt. T., M.P., F.L.S., G.S. &c. 30, Charles-street, St. James’s. Joyce, Thomas, Esq. F.G.S. &c. University College, Gower-street. Joyce, A. Esq. University College, Gower-st. Jukes, J. B. Esq. M.A., F.G.S. &c. Geolo- gical Survey, Craig’s-court, Charing Cross. Jury, S. H. Esq. Cotham, Bristol. Kay, James, Esq. University College, London. Kay, Robert, Esq. Bolton. Kay, William, Esq. F.L.S. &c. Royal Marine Barracks, Stonehouse, Plymouth. Keele, J. R. Esq. Portland-st. Southampton. Kelaart, — M.D. Fort Clarence, Rochester. Kell, William, Esq. Gateshead, near New- castle-on-Tyne. Kenyon, the Hon. Mrs., Parade, Shrewsbury. Kenyon, J. R. Esq. 7, Russell-square. King, W. Esq. Collingwood-st. Newcastle- on-Tyne. Knapp, Charles Esq. 5, Norfolk-crescent, Hyde Park. Koninck, L. de, Esq. Liége. Krantz, M. Berlin. Laing, A. L. Esq. Colchester. Landseer, George, Esq. Cunningham-place, St. John’s Wood. Langhorn, John, B. Esq. Richmond, York- shire. LIST OF MEMBERS. xi Langstaff, J. Esq. 9, Cambridge-square. Lankester, Edwin, M.D., F.R.S., L.S. 22, Old Burlington-street. Lawrence, John, Esq. F.G.S. Elton, Oundle. Leaby, Michael, M.D. Bridgend, Glamorgan- shire. Leckenby, Jno. Esq. Scarborough. Lecks, E. F. Esq. F.L.S. &c. 65, Chester-sq. Lee, John, LL.D., F.R.S., B.A.S. &c. 5, College, Doctor’s Commons. Lee, John, Esq. 2, Grove-villas, Camberwell- grove. Lee, Jno. Edward, Esq. The Priory, Caer- leon, Monmouthshire. Lee, Henry M. Esq. Whittlesea. Leeson, E, M.D. Greenwich. Leifchild, John R. Esq. 6, Great Camden- street, Camden Town. Lemon, Sir C. Bart. F.R.S., G.S. &c. 40, Charles-street. Leslie, James, Esq. Chanonry, Old Aber- deen. Lestourgeon, Charles, Esq, M.A. Trinity- street, Cambridge. Llewelyn, J. D. Esq. F.R.S. L.S. &c. Pentle- gare, Swansea. Llewellen, W. jun. Esq. F.G.S. &c. Ponty- pool. Lewis, Augustus, Esq. B.A. F.G.S. &c. 18, Stratford-place, Cavendish-square. Library of the University, King’s College, Aberdeen. Liddell, Andrew, Esq. Plean House, Glasgow. Liddell, Lieut. J. R.E. Portsmouth. Lidstone, Robert, Esq. Plymouth. Lingard, Jno. R. Esq. Greenbank House, Stockport. Lingwood, R. M. Esq. M.A., F.L.S. &c. Syston, near Ross, Hereford. Lister, J. J. Esq. F.R.S. &c. Upton, Essex. Lister, Jno., M.D., 20, Weymouth-street, Portland-place. Lister, Rev. William, Bushbury, Stafford- shire. Literary and Philosophical Society of Shef- field. Literary and Phijosophical Society of New- castle. Literary and Scientific Institution, Frome, Somersetshire, Lloyd, John, Esq. 77, Snow-hill. Lloyd, Dr. F.G.S. &c. Stank-hill, near War- wick. Loftus, W. K. Esq. Stand House, Newcastle- on-Tyne. Lomax, William G. Esq. Gilnow, Bolton-le- Moors._ Long, H. W. Esq. Rood Ashton, Trowbridge. Lonsdale, W. Esq. F.G.S. Keynsham, near Bath. Lowry, J. W. Esq. F.R.G.S. 45, Robert- street, Hampstead-road. Lubbock, Sir John W. Bart. M.A., F.R.S., L.S., Mansion-house-street. Ludlow Natural History Society. Lyell, Sir C. M.A., F.R.S., L.S., G.S. &e, 11, Harley-street, Cavendish-square. Mackeson, Henry B. Esq. F.G.S. &c. Hythe, Kent. Maclaren, Charles, Esq. F.R.S.E., G.S. &c. Northumberland-street, Edinburgh. Maclean, William C. Esq. Woodbridge. Macredie, P. B. M. Esq. Perceton Irvine, North Britain. Magendie, A. Esq. F.R.S.,G.S. &c. Heding- ham Castle, Castle Hedingham, Essex. Major, Charles, Esq. 21, Billiter-street. Mansell, Jno, Esq. Whatcomb House, Blandford. Mantell, G. A. Esq. LL.D., F.R.S., G.S. &c. 19, Chester-square, Pimlico. Marsh, John, Esq. Burnt Tree, near Dudley. Marshall, James G. Esq. M.P. Leeds. Marshall, Matthew, Esq. Bank of England. Martin, P. J. Esq. F.G.S. &c. Pulborough, Sussex, Martin, P. Esq. Reigate. Marrat, F. P. Esq.9, Lower Arcade, Liverpool. Masters, Peter, Esq. Reigate. Matthieson, James, Esq. 82, Bishopsgate- street Within. Mathews, W. jun. Esq. Park Hall, near Kidderminster. May, Charles, Esq. Ipswich. McAndrew, R. Esq. F.G.S, &c. Liverpool. McDermott,G.A. Esq. F.G.S. &c. Chesterton Hall, near Newcastle-under- Line. McIntosh, John, Esq. Milton Abbey. Meade, Rey. J. R. Castle Cary. Xil LIST OF MEMBERS. Mechanics’ Institution, Lewes. Mechanics’ Institution, Llandilo. Mechanical and Scientific Institution, Mor- peth. Mechanics’ Institution, Bolton. Medlock, Henry, Esq. Royal College of Chemistry, Hanover-square. Melville, Dr. A. G. British Museum. Meryon, Edward, M.D. 14, Clarges-street. Miller, George, M.R.C.S.E. &c. Emsworth. Miller, Hugh, Esq. Edinburgh. Mills, Mrs. Lexden Park, near Colchester. Mitchell, John, Esq. Church-street, Wol- verhampton. Mitchell, J. Esq. F.R.S. Mauchline. Moggridge, M. Esq. The Willows, Swansea. Montague, Lord Robert, Kimbolton Castle. Moore, J. C. Esq. Sec. G. S. &c. 4, Hyde Park Gate, Kensington. Morgan, James, Esq. 22, Fenton-square, Huddersfield. Morgan, Rev. William Leigh, Cardiff. Morgan, William, Esq. Swansea. Morris, John, Esq. F.G.S. Kensington. Morris, John, Esq. Belvedere, Bath. Morson, T. N. Esq. Southampton-row, Russell-square. Morton, J. Howard, M.D. Southampton. Morton, J. Highfield, Esq. 88, Grove-street, Liverpool. Mosley, Sir Oswald,Bart.,D.C.L.,F.LS.,GS. &c. Rolleston Hall, Burton-on-Trent. Murchison, Sir R. I., G.C.H.S., M.A, F.R.S., G.S., L.S. &c. 16, Belgrave- square. Murdock, William, M.D. 320, Rotherhithe. Murray, William, Esq. Monkland, Glasgow. Museum of Economic Geology, Craig’s- court, Charing Cross. Natural History Society, Manchester. Naturforschende Gesellschaft. Neale, Edward V. Esq. 66, South Audley-st. Neale, T. C. Esq. Chelmsford. Neeld, Joseph, Esq. M.P., F.L.S. &c. Grit- tleton House, Chippenham. Neison, Francis G. P. Esq. F.L.S. &c. 3a, St. James’s-square. Nelson, Capt. R. I., R.E. 7, Albert-street, Plymouth. Neville, R. J. Esq. F.G.S. &c. Llangennick Park, Swansea. Newman, Edward, Esq. F.L.S.&c. 9, Devon- shire-street, Bishopsgate-street. Nichol, Prof. I. P. Glasgow. Nicol, J. Esq. F.R.S.E. &c. Geological Society. Noble, W. H. Esq. Lieut. R.E. Chatham. Norfolk and Norwich Literary Institution. Northampton, The Marquis of, F.R.S., F.S.A., L.S., G.S. &e. 145, Piccadilly. Norton, J. H., M.D. &c. Shirley, near South- ampton. Norris, Henry, Esq. F.R.C.S. &c. South Petherton. Nunneley, Thomas, Esq. Leeds. Nunn, J. Esq. Kast Bergholt, Suffolk. O’Gorman, George, Esq. F.G.S. &c. 56, Baker street, Portman-square. Oldham, Prof. F.G.S. &c. 5, Trinity College, Dublin. Olivier, Lieut.-Col. H.S. Pottern Manor, Devizes. Ormerod, G. W., Esq. M.A., F.G.S. &c. Manchester. Onslow, M.E. Esq. Woodbridge House, near Guildford, Surrey. Owen, Prof. R., M.D., LL.D., F.R.S., L.S., G.S., &c. Royal College of Surgeons. Paine, J. M. Esq. Farnham. Papillon, Rev. J., Lexden. Parry, Thomas G. Esq. F.G.S. Highnam Court, near Gloucester. Pattisson, Mrs. Jacob, Witham, Essex. Pearson, Sir Edwin, K.H., M.A., F.R.S. &c. 5, Gloucester-terrace, Regent’s Park. Peckover, Algernon, Esq. F.L.S. Wisbeach. Penny, Charles, Esq. 19, Barrington-road, Brixton, Surrey. Pengelly, William, Esq. Torquay. Penruddock, Charles, Esq. Baverstoke House, near Salisbury. Percy, I., M.D., F.R.S. &c. Birmingham. Perkins, Rev. R. B. Wooton-under-Kdge, Gloucestershire. Perry, George, Esq. 39, Spencer-street, Northampton-square. Phillips, Prof. John, F.R.S., G.S. &c. York. Philosophical Society of Glasgow. LIST OF Philosophical Society, Leicester. Philpot, Miss, Lyme Regis. Pickering, John, Esq. 117, Lower Thames-st. Pickford, J. Esq. Brighton. Pidgeon, Jonathan, S. Esq.33, Myddelton-sq. Pigg, Thomas, jun., Esq. Newcastle. Pitts, R.C. Esq. 8, St. Giles’s-street, Norwich. Plant, James, Esq. 34, Sparkense-street, Leicester. Plomley, F., M.D., F.L.S. &c. Maidstone. Pollexfen, Rev. J. H., M.A. 4, Bedford-place, Clapham Rise. Portlock, Lieut.-Col., R.E., F.R.S., G.S., &c. Portsmouth. * Potts, Thomas, Esq. Hampton House, Tor- quay. Powles, T. W. Esq. York-place, Portman-sq. Pratt, S. P. Esq. F.R.S., G.S. &c. 55, Lin- coln’s-inn-fields. Preston Literary and Philosophical Institu- tion. Prestwich, Joseph, jun. Esq. F.G.S. Mark- lane. Prevost, J. L. Esq. 77. G.S. &c. 3, Suffolk- place, Pall Mall, East. Pritchard, Rev.C., M.A., F.R.S.&c. Clapham. Proudfoot, Thomas, M.D. Kendal. Prout, Rev. E., F.G.S. &c. 12, Champion Grove, Camberwell. Provis, William A. Esq. The Grange, Elles- mere, Salop. Pym, John A. Esq. The Hazells, Biggleswade. Quekett, John, Esq. Royal College of Sur- geons. Raban, Major, 33, Petersburgh-place, Bays- water. Radley, William C. Esq. M.R.C.S.L. Newton Abbot, Devonshire. Ralph, M. Esq. Bernard-street, Clifton. Ramsay, Prof. A. C., F.G.S. &c. Geological Survey, Craig’s-court, Charing Cross. Ramsey, Sir James, Bart. Banff. Ramsey, William, Prof. of Humanity, Uni- versity of Glasgow. Randolph, Rev. J. H., M.A., F.G.S. Sander- stead, Croydon. Rankin, R., M.D. Carluke, Glasgow. MEMBERS. Xl Ransome, Mrs. Robert, Ipswich. Ransome, George, Esq. F.L.S. &c. Ipswich. Raper, W. A., M.D., Parade, Portsmouth. Rawson, J. Esq. Green Ryde, near Halifax, Yorkshire. Reade, Rev. I. B., M.A., F.R.S. &c. Stone, near Aylesbury, Bucks. Redmond, M. Esq. 79, Hatton Garden. Reeve, Lovell, Esq. A.L.S. &c. King William- street, Strand. Reid, Professor John, St. Andrews, N. B. Richardson, W.S., F.G.S. &c. 3, Tanfield- court, Temple. Richardson, William, Esq. F.G.S. &c. 47, Bedford-row. Richardson, William, Esq. Southeram, near Halifax. Robertson, Alex. Esq. F.G.S. &c. Woodside Cottage, Elgin, N. B. Roddam, Jonathan, Esq. Newhouse, Wear- dale, Durham. Rogers, Prof. Henry D., F.G.S. &c. Phila- delphia, U. S. Rogerson, John, Esq. Newcastle-on-Tyne. Roper, F. C. S. Esq. 9, Clapton-square, Hackney. Rothery, H. C. Esq. M.A., F.L.S. 10, Strat- ford-place. Roots, William, M.D., F.S.A. &c. Surbiton, Kingston, Surrey. Rofe, John, Esq. F.G.S. &c. Preston. Rose, C. B. Esq. F.G.S. &c. Swaffham. Rosling, A. Esq. Camberwell-terrace, Cam- berwell. Round, George, Esq. Colchester. Royal Agricultural Coll. Library, Cirencester. Royal College of Surgeons. Royal Geological Society of Cornwall, Pen- zance. Royal Institution, Liverpool. Royal Institution of South Wales, Swansea. Royal Military College, Sandhurst, Bagshot. Ruskin, John, Esq. F.G.S. &c. Denmark- hill, Camberwell. Ruthven, John, Esq. Kendal. Rutter, John, Esq. Ilminster. Sabine, Lieut.-Col. R.A, F.R.S., GS. Athenzeum Club. Salmon, J. D. Esq. Godalming. XIV LIST OF MEMBERS. Salter, J. W. Esq. F.G.S. &c. Museum of Economic Geology, Craig’s-court, Cha- ring Cross. Sanders, W. Esq. F.G.S. &c. Clevedon, Bristol. Sandwith, Thos. M.D. Beverley, Yorkshire. Saunders, G. H. Esq. F.G.S. &c. Cowley- street, Westminster. Saunders, T. W. Esq. 6, Charing Cross. Saunders, W. Wilson, Esq. F.L.S. &c. Lloyds. Saxby, S. M. Esq. Mountfield, Bonchurch, Isle of Wight. Sayle, George, Esq. Kingstaith-square, Lynn, Norfolk. Scott, J. B. Esq. M.A. Bungay, Suffolk. Scott, Dr. W. R. St. Leonards, Exeter. Scott, Lieut. R. KE. 7, Dundas-terrace, Wool- wich. Sedgwick, Rev. Adam, M.A., F.R.S.,G.8. &c. Cambridge. Selwyn, A. R. Esq. Geological Survey, Cryaig’s-court, Charing Cross. Sharp, Samuel, Esq. Stamford. Sharpe, Daniel, Esq. F.L.S., G.S. &c. 2, Adelphi-terrace. Sharpe, John, Esq. Culverden Castle, Ton- bridge Wells. Shaw, John, M.D., F.G.S., &c. Hop House, Boston, Lincolnshire. Sheppard, T. Byard, Esq. Selwood Cottage, Frome. Sims, W. D. Esq. Ipswich. Sinclair, Lady, Pilmuir, Torquay. Sismonda, M. Angelo, Prof. of Mineralogy, Turin. Sissons, Richard, Esq. Huddersfield. Simpson, Samuel, Esq. The Greaves, Lan- caster. Sloper, George E, Esq. Devizes. Smith, James, Esq. F.R.S.L. & E., G.S. Jordan-hill, near Glasgow. Smith, J. Toulmin, Esq. F.G.S. &c. 8, Ser- jeants’ Inn, Fleet-street. Smith, J. Orton, Esq. 8, Serjeants’ Inn, Fleet-street. Smith, W. H. Esq. 4, Devonshire-street, Queen’s-square. Smith, W. W. Esq. M.A. Smith, Rev. J. Pye, D.D., LL.D., F.R.S., G.S. &c, Homerton College. Smith, Captain Robert, Windy Arbour, Dundrum. Smith, Samuel ,Esq. Wisbeach. Smyth, W. H. Esq. South Elkington, Louth. Sopwith, T. Esq. F.R.S., G.S. &c. 1, Chapel- place, Duke-street, Westminster. Sorby, H. C. Esq. Woodbourne, Attercliffe, near Sheffield. Sowerby, James de Carle, Esq. F.LS. &c. Royal Botanic Gardens, Regent’s Park. Sowerby, George B. jun. Esq. F.L.S. &c. 70, Great Russell-street, Bloomsbury. Spence, W. Esq. Pres. Eut. Soc. F.R.S., LS. &c. 18, Lower Seymour-street. Spencer, — Esq. Bowood, Wilts. Spencer, John, Esq. Calne, Wilts. Spooner, EK. O. Esq. Blandford, Dorset- shire. Spragge, W. K. Esq. Torquay, Spratt, Thomas, Esq. Com. R.N., F.G.S. &c. Tynemouth, Devon. Spriggs, William, jun. Esq. Broad-street, Worcester. Stamford Institution. Stansfield, James, Esq. Halifax. Stark, W. Esq. F.G.S. &c. Norwich. Stavordale, Lord, 31, Old Burlington- street. Steel, C. Wilson, Esq. Lewisham. Steele, James, Esq. Rector of the Royal Academy, Inverness. Stevens, H. Esq. The Shaws, Matlock, Derbyshire. Stevens, H. Esq. F.G.S. &c. Duffield, near Derby. Stewart, R. Esq. Torquay. Stokes, Charles, Esq. F.R.S., L.S., G.S. &c. 4, Verulam-buildings, Gray’s Inn. Strickland, H. E. Esq. M.A., F.G.S. &c. The Lodge, Tewkesbury. Stuchbury, Samuel, Esq. A.L.S., Bristol. Stutfield, W. Esq. F.G.S. &c. 1, Montague- place, Russell-square. Sunderland Corporation Museum. Sunderland Subscription Library. Surrey Nat. Hist. Society, Guildford. Swiney, John, M.D. Westall House, Chel- tenham. F.G.S. &c. LIST OF MEMBERS. XV Talbot, C. R. M., Esq. M.P., F.R.S. &c. Margam, Glamorgan. Tanner, William, Esq. Bristol. Tate, George, Esq. F.G.S. &c. Alnwick. Tayler, James, Esq. Marsden, near Hud- dersfield. Taylor, John, Esq. F.R.S., L.S. &c. Sheffield House, Church-street, Kensington. Taylor, Richard, Esq. Penmaer, Falmouth. Taylor, S. Watson, Esq. Urchfont, Devizes. Taylor, Henry, Esq. Brunswick House, Brixton. Teale, T. P. Esq. F.R.C.S.E. Leeds Tennant, Jas. Esq. F.G.S. &c. 149, Strand, (two copies). Teschemacher, Frederick, Esq. 4, Park-ter- race, Highbury. Thomas, W. L. Esq. Lieut. R.N. H.M.S. Mastiff. Thompson, Miss 8S. Stamford. Thomson, Alexander, Esq. F.R.S.E. Ban- chory House, Aberdeen. Thomson, J. Esq. F.R.S., G.S. &c. Primrose, near Clitheroe. Thornewill, Robert, Esq. Burton-on-Trent. Thornton, Rev. John, M.A., F.G.S, &c. Kim- bolton. Thorpe, Rev. W. M.A., F.G.S. &c. Wor- mesley Vicarage, Pontefract. Thurlow, Right Hon. Lord, Ashfield Lodge, Stowmarket, Suffolk. Tillard, Miss, Hastings. Tite, W. Esq. F.R.S., S.A., G.S. &c. 25, Upper Bedford-place, Russell-square. Tite, S. C. Esq. Towcester, Northampton- shire. Todd, R. B., M.D., F.R.S. &c. 3, New-street, Spring-gardens, Tomes, R. F. Esq. Welford, near Stratford- on-Avon. Tomkins, Chas. M.D., F.L.S. &c. Abingdon. Torquay Natural History Society. Tovey, R. Esq. 19, Blechynden-terrace, Southampton. Townsend, Mrs. E. M. Spring Field, Nor- wood. Trimmer, Joshua, Esq. F.G.S.&c. Magdalen- street, Norwich. Turner, H. N. Esq. 1, Upper Belgrave-place. Tweedy, M. Esq. Alverton, Truro. Twining, W., M.D., F.G.S. &c. 13, Bedford- place, Russell-square. Tylor, Alfred, Esq. F.G.S. Warwick-lane, Newgate-street. University of Glasgow. University Library, St. Andrews, Upsala University Library. Vallance, Edmund, Esq. Brighton. Vetch, Captain J. R.V., F.R.S., GS. &c. Truro. Vint, H. Esq. Colchester. Vint, Robert, Esq. Sunderland. Vienna, Imperial Library of Vivian, J. H. Esq. M.P., F.R.S., G.S. &c. Swansea. Von Buch, His Excellency M. Berlin. Wainwright, H. M. Esq. Dudley. Waldron, James, Esq. Hartswell, Wivelis- combe, Somersetshire. Walker, David, M.A., F.G.S. &c. Agricul- tural College, Maidstone. Walker, Charles, Esq. Collingwood, Torquay. Waller, Edward, Esq. Finnoe House, Bur- risokane, Ireland. Waller, Edw. Esq. Lessenderry, Aughnacloy. Walton, William, Esq. London Dock Head. Ward, N. B. Esq. F.L.S. &c. Wellclose-sq. Waring, Alfred, Esq. Hallenbrook House, near Bristol. Watts, John King, Esq. St. Ives, Huntingdon. Watts, S. T. Esq. Weymouth. Wauchope, Captain, R.N. Dacre, Penrith. Weiss, Prof. University, Berlin. Welsh, Robert, Esq. Huddersfield. Westall, Edward, Esq. Croydon. Wetherell, N. T. Esq. F.G.S. &c. Highgate. Whatman, J., Esq. M.A., F.R.S. Vinters Boxley, near Maidstone. Whewell, Rev. William, B.D., F.R.S., Hon. M.R.LA., F.S.A., F.G.S., F.R.A.S. Mast. Trin. Coll. Camb. Lodge, Cambridge. White, Aifred, Esq. F.L.S. &c. 19, Tindall- place, Islington. White, J. G., M.D. 18, Wharton-street, Pen- tonville. White, H.C. Esq. F.G.S. St. Heliers, Jersey. Whiting, J. B, Esq. King’s Lynn, Norfolk. XV1 LIST OF Whitmore, Wm. Esq. 2, Basinghall-street. Widdrington, S. EK. Capt. R.N., F.RS., G.S. &c. Newton Hall, Felton. Wiggins, John, Esq. F.G.S. 30, Tavistock-pl. Willcock, J. W. Esq. 6, Stone-buildings, Lincoln’s Inn. Williams, Rev. D. F.G.S. &c. Bleadon, near Wells, Somerset. Williams, Dr. Swansea. Wills, William Esq. Edgbaston, Birmingham. Wilson, D. Esq. 5, St. Nicholas-street, Aber- deen. Wilson, Prof. John F.R.S.E., F.G.S. Royal Agricultural College, Cirencester. Wilson, Jas. Esq. Wadham Coll. Oxford. Wilson, J. H. Esq. Staveley. Wilson, Edward Esq. F.G.S. &c. Lydstip House, near Tenby, S. Wales. Wilson, Hon. and Rev. R., F.G.S. &c. Wymondeham, Norwich. Wilson, Sumner, Esq. 1, Cranbury-terrace, Southampton. Wilson, William, Esq. Oak Hill, Torquay. Wilton, John W. Esq. Gloucester. Witts, Rev. E. F. Stanway, near Winchcomb. Winstone, Benjamin, M.D. 20, Bouverie- street, Fleet-street. MEMBERS. Wintle, G.S. Esq. East Gate-st. Gloucester. Wollaston, Miss H. Clapham-common. Wolley, Chas. Esq. King’s Coll. Cambridge. Wood, Mrs. Col. Rectory House, Wrekham, Bishops Witham. Wood, 8. A.M., M.D. &c. Avenue House, Bandon. Wood, Edward, Esq. Richmond, Yorkshire. Wood, S. V. Esq. F.G.S. &c. 28, Fortess- terrace, Kentish-town. Woodd, C. H. L. Esq. F.G.S. F.S.A. &c. Hillfield, Hampstead. Woods, 8S. jun. Esq. 9, Tower Chambers, Liverpool. Woodward, Charles, Esq. F.R.S. 10, Comp- ton-terrace, Islington. Worcestershire Natural Hist. Soc. Foregate, Worcester. Wright, Thomas, M.D. Cheltenham. Wyke, Wm. Beadon, Esq. Churchstanton, Honiton, Devon. Yates, James, Esq. M.A., F.R.S., L.S., G.S. &c. Lauderdale House, Highgate. Young, J. Forbes, M.D., F.L.S. &c. Upper Kennington-lane. MONOGRAPH ON THE FOSSIL REPTILIA OF THE LONDON CLAY. OrvER.—CHELONTIA. Family—Mar ina. Genus— CHELONE. THE majority of the Fossil Chelonians of the Eocene tertiary deposits, defined or described in my ‘ Report on British Fossil Reptiles,’ belonged to the marine division of the order, and to the genus Che/one ; and as the species of this genus depart least from the ordinary reptilian type in the modification of the bones of the trunk, composing the characteristic thoracic-abdominal case of the order, I propose to commence with them those descriptions of the Chelonian reptiles which fall to my share of the present Monograph. In order to facilitate the comprehension of the descriptions and figures of the fossil Chelonians, a brief notice is premised of the composition and homologies of the carapace and plastron, or roof and floor, of that smgular portable abode, with which the reptiles of the present order have been endowed in compensation for their inferior powers of locomotion or other modes of escape or defence. In the marine species of the Chelonian order, of which the Chelone mydas may be regarded as the type, the ossification of the carapace and plastron is less complete, and the whole skeleton is hghter than in those species that live and move on dry land: but the head is proportionally larger—a character common to aquatic animals,— and being incapable of retraction within the carapace, ossification extends in the direction of the fascia, covering the temporal muscles, and forms a second bony covering of the cranial cavity: it is interesting to observe, however, that this accessory defence is not formed by the intercalation of any new bones, but is due to exogenous growth from the frontals (11), parietal (7), postfrontals (12), and mastoids (8, see T. I, OTT, XY): The bony carapace is composed externally of a series of median and symmetrical pieces (fig. 1, c/, si—si1, py), and of two series of unsymmetrical pieces ( p/1—8, m1—12) on each side. The median pieces have been regarded as lateral expansions of the summits of the upper vertebral (neural) spines,* the median lateral pieces as similar * Cuvier, Lecons d’ Anatomie Comparée, tom. i (1799), p. 212. 2 FOSSIL REPTILIA OF THE LONDON CLAY, ~ developments of the vertebral ribs (pleurapophyses),* and the marginal pieces as the homologues of the sternal ribs (heemapophyses).t I must refer the reader to my Memoir, communicated to the Royal Society, for the facts and arguments which have led me to regard these pieces, as dermal ossifications, homologous with those that support the nuchal and dorsal epidermal scutes in the crocodile. Most of the bony pieces of the carapace are, however, directly continuous, and connate,{ with the obvious elements of the vertebrae, which have been supposed exclusively to form them by their unusual development; the median pieces have accordingly been called “vertebral plates,” and the medio-lateral pieces “ costal plates.” I retain the latter name, although with the understanding and conviction that they are essentially or homologically distinct parts from the vertebral ribs or pleurapophyses with which they are connate and more or less blended. But, with regard to the term “vertebral” plate, since the ribs (cosf@) are as essentially elements of the vertebra as the spinous processes themselves, I have been in the habit, in my Lectures, of indicating the median series by the term “ neural plates,” which term has the further advantage of removing any ambiguity from the descriptions that might arise from their being mistaken for the superincumbent epidermal shields, which are likewise called “ vertebral plates” in some English works.{ The term “marginal” is retained for the osseous plates forming the periphery of the carapace; but the median and symmetrical ones, which seem also to begin and end the “ neural” series, are specified, the one by the term “nuchal plate,” the other by that of ‘* pygal plate.” The “neural plates” are numbered as in the classical Monograph of Bojanus.|| In the subjoined woodcut of the carapace of the loggerhead turtle (Chelone caouwanna) (fig. 1), ch is the nuchal plate ; s1 to s11 the neural plates ; pli to pls the costal plates ; and m\ to m2 the marginal plates. The carapace is impressed by the superimposed epidermal scutes or shields, which consist of a median series, called “ vertebral scutes” vi to v5; * Tbid. p. 211. Rathké has recently supported this determination by arguments drawn from the mode of development of the carapace. See ‘ Annales des Sciences Naturelles,’ Mars, 1846; and ‘ Ueber die Entwickelung der Schildkroten,’ 4to, 1848, where he says, p. 105 :—‘** Ausser den Rippen und den horizontal liegenden Tafeln, zu welchen sich die Dornfortsiitze des zweiten und der sechs folgenden Riickenwirbel ausbilden, dienen bei den erwachsenen Schildkroten zur Zusammensetzung des Riickenschildes noch eine oder mehrere Knochenplatten,” viz. the ‘marginal plates.” I have shown how Rathké was deceived by over-estimating the character of connation, in my ‘Observations on the Development of the Carapace and Plastron of the Chelonians,’ which conduct to a different conclusion to that at which Cuvier and Rathké have arrived. (Philosoph. Transactions, 1849.) + Geoffroy, Annales du Museum, tom. xiv (1809), p. 7. t This term is used in the definite sense explained in my work on the ‘ Archetype of the Vertebrate Skeleton’ (8vo, V. Voorst, p. 49), as signifying those essentially different parts which are not physically distinct at any stage of development; and in contradistinction to the term “ confluent,’’ which applies to those united parts which were originally distinct. § See Griffiths’s translation of Cuvier, vol. ix, Synopsis of Reptilia, p. 6—<‘fifth vertebral plates prominent.” || Anatome Testudinis Europzee, fol. 1821, tab. iti and iv. CHELONIA. 3 and of a lateral series of “ costal scutes ;” there is also a peripheral series of “‘ marginal scutes” corresponding with and impressing the mar- ginal plates. The nuchal plate (cd) is remarkable for its breadth in all Chelonia, and usually sends down a ridge from the middle line of its under surface, which is attached by ligament to the summit of the neural arch of the first dorsal vertebra. The first true neural plate, s1, is much narrower, and is connate with the summit of the neural spme of the second dorsal vertebra; the succeeding vertebral neural plates, s2—ss, have the same relations with the succeeding neural spines, but the ninth, tenth, and eleventh, like the nuchal (ch) and pygal (py), plates are independent ossifications in the substance of the derm. The costal pieces of the carapace are supra-additions to eight pairs of pleurapophyses or vertebral ribs, those, viz. of the second to the ninth dorsal vertebree inclusive. The slender or normal portions of the ribs project freely for some distance beyond the expanded and connate portions (“ costal plates” of the carapace), along the under surface of which the rib may be traced, of its ordinary breadth, to the neck and head, which liberates itself from the costal plate to articulate to the interspace of the two contiguous vertebral bodies, (centrums), to the posterior of which such rib properly belongs. The woodcut (fig. 2) illustrates this structure: ch shows the inner side of Carapace of the Loggerhead Turtle (Chelone caouanna). the nuchal plate; ci is the first rib, articulated to the fore part of the body of the first dorsal vertebree; p/) is the first rib of the carapace (the second rib of the dorsal series), connate with the Inner view of carapace of the Loggerhead Turtle first costal plate; pl2 to pls, are the (Chelone caouanna). succeeding ribs and costal plates of the carapace. The heads of the ribs articulate to A FOSSIL REPTILIA OF THE LONDON CLAY. the interspaces between their own vertebral body, and that of the preceding vertebra. The tenth vertebra supports a short pair of ribs in Chelone and in Hmys, but not in Trionyx; and this vertebra is commonly reckoned as a “lumbar” one. The eleventh and twelfth vertebree have short and thick ribs, which abut against the iliac bones, and they are regarded as forming the sacrum. The remaining vertebree belong to the tail, and are “caudal.” The costal plates articulate with each other, and with the neural plates by fine dentated sutures. The free extremities of the ribs are implanted into sockets of those marginal plates which are opposite to them. The Ist, 2d, 3d, and 10th, are not so articulated in the loggerhead turtle. But all the marginal plates articulate with each other, and with the nuchal (c/) and pygal (py) plates by sutures. The osseous basis of the plastron consists of nine pieces, one single and sym- metrical, the rest in pairs. The median piece, s, is the extosterna/; the anterior pair, es, is the episternal ; the second pair, /s, the hyosternal; the third pair, ps, the hyposternal; and the posterior pair, vs, the xriphsternal. With regard to the nature or homologies of these bones, three views have been Fig. 3. taken. The one generally adopted, on the authority : of Cuvier, Bojanus, and Geoffroy St. Hilaire, is, that the nine bones of the plastron are subdivisions of a vastly expanded sternum, or breast-bone; the second view is, that these subdivisions of the sternum are enlarged by combination with ossifications of the in- tegument ;* and the third view, in which Rathke stands alone, is, that they are exclusively dermal bones, and have no homologues in the endoskeleton of other vertebrata.t Since this opinion is given as the result of that celebrated embryologist’s observations on the de- velopment of the Chelonian reptiles, I have tested it Bones of the plastron of the Loggerhead by a series of similar researches on the embryos and SHORT Helos eaonarey) young of the Chelone mydas and Testudo indica, and have been Jed by them to conclusions distinct from any of the three theories above cited. The sternum, like the carapace, is, without doubt, a compound of connate, endo- skeletal and exoskeletal pieces; but the endoskeletal parts are not exclusively the homologues of the sternum. For the details of the observations, and the special arguments on which these conclusions are founded, I must refer to my paper in the ‘Transactions of the Royal Society, 1849; the homologies of the endoskeletal parts of the plastron will require a brief illustration here from comparative anatomy. * Peters, Observationes ad Anatomiam Cheloniorum, 1838. + Ueber die Entwickelung der Schildkroten, 4to, 1848, p. 122. CHELONIA. 5 Geoffroy St. Hilaire, whose views are generally adopted, was guided in his deter- mination of the parts of the plastron by the analogy of the skeleton of the bird: which analogy may be illustrated by the subjoimed dia- grams of corresponding segments of the thorax of a bird (fig. 4) and of a tortoise (fig. 5). In a(\ //pt pr\ ja both figures cis the centrum or vertebral body ; as the neural arch and spine ; compressed in the bird, depressed and laterally expanded, accord- ing to Geoffroy, in the tortoise ; p/ the pleura- pophysis, or vertebral rib, expanded in the tortoise, and with its broad tubercle articu- lating with the expanded spine; 4; /’ in fig. 5, answers to / in fig. 4, and is the hamapo- physis (sternal rib, or ossified cartilage of the rib); 4, ds in fig. 5, is As in fig. 4, i. e. exclusively a sternum, with the entosternal piece, 4s’, developed hori- zontally in the tortoise, and vertically m the bird. The prima facie simplicity of this view has imposed upon most comparative anatomists: and _ yet there are other vertebrate animals more nearly allied to the Chelonia than birds, and with which, therefore, comparison should have been insti- tuted before general consent was wy ah 2 : “eas r yielded to the Geoffroyan hypothesis. Thoracic segment of the skeleton of a Tortoise. If, e. g. we take the segment of a crocodile’s skeleton (fig. 6) corresponding with that of the tortoise (fig. 5), the comparison will yield the following interpretation: in both figures c is the centrum: zs the neural arch and spine, with d@ the diapophysis; sc a median dermal bony plate (connate with ws in the tortoise) ; pl the pleurapophysis; se sc lateral dermal bony plates (connate with p/ in the tortoise); A, i’ in fig. 5, answers to /’ in fig. 6, an intercalated, semi-ossified piece between p/ and / in the crocodile; 4, fs in fig. 5, answers to 4, the haemapophysis in the crocodile; and fs in — Thoracic segment of the skeleton of a Crocodile. fig. 5, exclusively represents /s, the sternum in the crocodile. 6 FOSSIL REPTILIA OF THE LONDON CLAY. Such a comparison, in my opinion, guides us to a truer view of the homologies of the thoracic-abdominal bony case of the Chelonians, especially with regard to the lateral or parial pieces of the plastron, than the comparison exclusively relied on by Geoffroy St. Hilaire. The Plesiosaurus, by its long and flexible neck, small head, expanded coracoid and pubis, and flattened bones of the paddles, comes much nearer to the turtle than the crocodile does; and its abdominal ribs, or hemapophyses, are more developed than in the crocodiles; a comparison of the ventral surface of the skeleton, such as that figured by Dr. Buckland, in his ‘ Bridgewater Treatise,’ vol. ii, pl. 18, fig. 3, will show how clearly those abdominal ribs would correspond with the hyosternals and hyposternals of the turtle, if they had coalesced together at their middle parts, leaving their outer and inner extremities free. With regard to the marginal pieces mi—mi2, figs. 1 and 2, although the comparisons illustrated by figs. 4, 5, 6, show that they answer rather to the intercalated piece /’ in the crocodile than to the entire sternal rib 4 in the bird; yet the phenomena of their development demonstrate that they are exclusively bones of the dermal skeleton, retaining their freedom from anchylosis with the endoskeletal elements, like the nuchal, pygal, and last three neural plates (ch, py, s9, s10, and s11, fig. 1). This insight into their true nature teaches why they do not correspond in number with the vertebral ribs or pleurapophyses (p/i—vpis, fig. 2). In the loggerhead turtle, for example, the first three and the tenth (#1, m2, m3, and m0) have no corresponding pleur- apophyses articulating with them; and if even c1 be supposed to correspond to m3, there are no rudiments of ribs answering to m1 and m2. The marginal plates are not constant in number; the Chelone mydas has two less than the Chelone caouanna has. Some species of Zrionyx (Cryptopus, Dum. and Bibron) have a greater number, but of smaller and less regular size, confined to the posterior part of the limb of the carapace; in other species of Zrionye (Gymnopus, Dum. and Bibron), and in Sphargis, the marginal part of the carapace retains its embryonic condition in all Chelonia, as a stratum of cartilaginous cells in the substance of the derm, forming the thickened, flexible border of the carapace. The rudiments of the hyosternals and hyposternals have originally the form of sternal or abdominal ribs ; extend transversely, and rise at their outer extremities to join those of the first and sixth pair of vertebral ribs, completing the hzemal, or inferior vertebral arch, without the interposition of any of the marginal pieces, which are merely applied to the outer sides of the hemapophysis or sternal ribs. The expansion of the parts of the plastron, especially in the fresh-water and land tortoises, is due chiefly to the ossification of a layer of cartilage-cells in the substance of the derm, which ossified plates are connate with the more internal elements of the plastron, representing the sternum‘and sternal ribs. In the following descriptions of the fossil Chelonia, the terms ‘ entosternal, episternal, hyosternal, hyposternal,’ and ‘ xiphisternal,’ will be used as absolute designations of the combined endoskeletal and exoskeletal bones of the plastron, without implying assent to the hypothesis that first suggested those names to Geoffroy St. Hilaire. CHELONIA. - 7 The scapular and pelvic arches, and the bones of the extremities of the Okhelonia, are described and figured in the ‘Ossemens Fossiles’ of Cuvier ;* where, also, the figures of the modifications of the carapace and plastron, in the fresh-water and land tortoises, will suffice for the purpose of ulterior comparisons with the fossils described in the present work, if they be understood according to the homologies above discussed, and which are illustrated by the figures 1 and 2 of the carapace, and fig. 3 of the plastron of the Chelone caouanna. With regard to the more immediate subjects of the present Monograph, it must be admitted that the important generalizations of Cuvier and Dr. Bucklandt have been confirmed, but not materially extended, by subsequent observations on the remains of reptiles of the Chelonian order. Cuvier, after admitting that his results in regard to the tortoises were not so precise as those relating to the crocodiles, sums up his chapter on the fossil Cie/onia in the following words : ‘‘ Toutefois nous avons pu nous assurer que les tortues sont aussi anciennes dans le monde que les crocodiles ; qu’elles les accompagnent généralement, et que le plus grand nombre de leurs débris appartenant a des sous-genres dont les espéces sont propres aux eaux douces ou 4 la terre ferme, elles confirment les conjectures que les os de crocodiles avoient fait naitre sur l’existence diles ou de continens nourissant des reptiles, avant qu'il y ait eu des quadrupédes vivipares, ou du moins avant quils aient été assez nombreux pour laisser une quantité de débris comparable a ceux des reptiles.”¢ Dr. Buckland also states, in general but precise terms, that “ the Chelonian reptiles came into existence nearly at the same time with the order of Saurians, and have continued coextensively with them through the secondary and tertiary formations unto the present time. Their fossil remains present also the same threefold divisions that exist among modern Chelonia into groups. respectively adapted to live on land, in fresh water, or the sea.” The remains of sea turtles (Chelone) have been recognised in the Muschelkalk, the Wealden, the lower cretaceous formation at Glaris, and the upper chalk-beds at Maestricht. Figures of Chelonites, as that in the Frontispiece to Woodward’s ‘Synoptical Table of British Organic Remains,’ and in Konig’s ‘Icones Sectiles’ (pl. xvii, fig. 232, @ and 4), have been published; but no true marine Chelonian, from Eocene strata, had been scientifically determined prior to the communication of my Paper on that subject to the Geological Society of London.|| All the Chelonites from Sheppey, described and figured in the last edition of Cuvier’s ‘Ossemens Fossiles,’ for * Tom. v, pt. 2, pl. xii and xiii. + Bridgewater Treatise (1836), p. 256. t Ossemens Fossiles, 4to, tom. v, pt. ii, p. 249. § Bridgewater Treatise, p. 256. || Proceedings of the Geological Society of London, vol. iui, pt. ii, p. 570, December 1, 1841. 8 FOSSIL REPTILIA OF THE LONDON CLAY. example, are referred to the fresh-water genus L’mys; and the statement in the earlier edition of the ‘Ossemens Fossiles,’ that the greater part of the remains of Chelonian reptiles belong to the fresh-water or terrestrial genera, is repeated. The aim of the Memoir, communicated to the Geological Society in December, 1841, was to show that the conclusion deduced by Cuvier, from an imperfect carapace from Sheppey, which might probably have belonged to a species of Hmys, had been unduly extended to other Chelonites, which undoubtedly belonged to the marine genus Chelone ; and that this genus was represented, in the Eocene strata, by at least six species ; the remains of five of which were from the London Clay at Sheppey, and those of a sixth were tolerably abundant in the cliffs near Harwich. In the carapace of the fossil Chelonian from Sheppey, communicated by Mr. Crowe, of Faversham, to Cuvier, and figured in the ‘ Ossemens Fossiles’ (tom. v, part 2, pl. xv, fig. 12), the author of that great work conceived that all the characters of the genus Himys were perfectly recognisable. He points out the proportions of the neural plates, which are as long as they are large; and in the figure they are represented of nearly a quadrate form, and not rhomboidal. The fifth neural plate in the fragment figured (probably the eighth) is separated from the sixth (ninth) by a point, which is made by the mesial ends of the fifth (probably the seventh) pair of costal plates; a structure which Cuvier says slightly recalls what he had observed in the Jura Hmys of Soleure.* But Cuvier admits that the neural plates (plaques vertébrales) are narrower than those of existing Hmydes ; and that the equal breadth of the ribs is a character common to the Chelones with the Hmydes. Now, in reference to the carapace figured by Cuvier, it is to be observed, that the margins are wanting; and that the broad conjomed portions of the costal plates are not longer than they might have been, had the fossil belonged to a turtle (Chelone) ; and, consequently, that there is no proof that they were united together by suture throughout their whole extent, as in the Hmydes ; but that they might have terminated in narrow tooth-like processes, as in the Chelones. The narrowness of the neural plates is a character which, with their smoothness, undoubtedly approximates the fossil to the Che/ones ; and, without intending to affirm that the fossil in question does not belong to the family Aimydide, which unquestionably existed at the time of the deposition of the Sheppey clay, its determination appears to me to be much less decisive than might be inferred from the remarks in the ‘ Ossemens Fossiles.’ * Tom. cit., p. 234. This structure is not, however, peculiar to the genus Hmys ; in the carapace of the Chelone caouanna, in the Museum of the Royal College of Surgeons, the seventh neural plate is separated from the eighth by the junction of the expanded extremity of the seventh rib on one side with that of the opposite rib, and the eighth neural plate from the ninth by the same modification of the eighth pair of ribs. A similar modification may also be seen in the carapace of the Trionya Henrici, T. XVI. CHELONIA. 9 Mr. Parkinson describes the plastron of a Sheppey Chelonite,* in which the hyosternal and hyposternal pieces are not united, but leave a vacancy in the middle, which ‘he conjectured may have been filled up by membrane. This specimen must have belonged to a specimen at least four inches in length, exclusive of the head and neck. But Cuvier supposes that it may, nevertheless, have belonged to an Fimys ; and that the vacancy of the bony sternum merely indicated the nonage of the individual.t The grounds on which Cuvier refers to the genus Hmys, the imperfect and dislocated carapace and plastron of M. Bourdet’s Sheppey Chelonite,t are not detailed; but it is evident that the hyposternals in that specimen are in contact at the posterior moiety of their median margins only; and that the margins recede anteriorly, leaving a median interspace; which, as the plastron is nearly a foot in length, can hardly be attributed to the immature state of the individual. And if, as Cuvier supposes, this specimen belongs to the same species as those in the collections of Messrs. Crowe and Parkinson, the same objection to their belonging to a fresh-water tortoise holds good , as to the one figured by M. Bourdet. The question of the reference of these Eocene fossils to the fresh- or sea-water families of the Chelonian order, seems to me to admit of the safest determination by examining the crania of the Sheppey Chelonites; since the differences in the extent - to which the temporal fossze are protected by bone, and in the proportions in which the bones enter into the formation of that covering, are strongly marked in the genera Emys and Chelone. But here Cuvier appears to have been unusually biassed in favour of the Emydian nature of the Sheppey fossils; for in reference to the cranium, figured by Mr. Parkinson, the affinities of which to the turtle’s skull will be presently pointed out, Cuvier observes : “elle est probablement aussi d’une Emyde, bien qu’elle participe des caractcres de Tortues de Mer, par la maniére dont le parietal recouvre sa tempe ; mais nous avons vu que 7’ Hmys expansa differe tres peu de Tortues de Mer a cet égard, et la partie antérieure de la téte fossile ressemble d’avantage a celle d’une Emyde qu’ a celle d'une Chelonée, surtout par le peu de largeur de l’intervalle des yeux.’’§ Now the most striking difference between the temporal bony vault of the “mys expansa and that of any known species of Chelone, is seen in the diminutive size of the post-frontals in this exceptional case among the Hmydes, as contrasted with their large size and actual extension over the temporal fossze in the Che/ones :—and this difference is accompanied by a proportional diminution in the breadth of the parietals in the true marine turtles. * Organic Remains, vol. ili, p. 268, pl. xviii, fig. 2. + Ossemens Fossiles, tom. v, pt. ii, p. 235. t Tom. cit., pl. xv, figs. 14-15. § Tom. cit., p. 235. 10 FOSSIL REPTILIA OF THE LONDON CLAY. But the figure in Parkinson’s work gives clearly the latter character ; whence also we may infer that it agreed more with the C/e/ones also in the size of the postfrontals ; although the anatomy of the skull is too obscurely delineated to demonstrate this fact. The following important affinities are, however, unquestionably indicated in Parkinson’s figure :—/irst, the large size of the orbits, which are nearly six times greater than those of the Limys eapansa; secondly, their more posterior and lateral position; and ¢hirdly, the greater breadth of the interorbital space: in all which characters the Sheppey fossil closely resembles the true Chelones, and differs from the only known species of mys (Podocnemys) eaxpansa, in which the temporal openings are protected by a bony roof. That fresh-water tortoises have left their bony cuirasses in the Sheppey clay, will be subsequently shown; but the evidence of the genus mys, adduced by Cuvier, is incompetent to prove their existence; and, it may be affirmed, that of the fossils cited by the founder of Paleontology, some, with great probability, and others with certainty, are referable to the marine genus, Che/one. Without further discussing the question as regards these evidences, I shall proceed to describe the specimens from Sheppey which I have myself had the opportunity of examining; and shall commence with those which belong undoubtedly to the marine family. CHELONE BREVICEPS. Owen. Tabule I and II. Proceedings of the Geological Society, December 1, 1841; Report on British Fossil Reptiles, Trans. British Association, 1841, p. 178. Syn. Emys Parxinsonir. J. E. Gray. — ove Sueprey. #. v. Meyer (?). CHELONE ANTIQUA. Keenig (‘). The first of the Chelonites, which led me to the recognition of this species, was a nearly perfect cranium from Sheppey (Tab. I, figs. 1—4), wanting only the occipital spine, and presenting a strong and uninterrupted roof, extended posteriorly from the parietal spine on each side (7, 7), over the temporal openings to the mastoids (8, 8) ; and formed anteriorly by a great development of the posterior frontals (22). This unequivocal testimony of the marine genus of the fossil, is accompanied by similar evidence afforded by the large size and lateral aspect of the orbits, the posterior boundary of which extends beyond the anterior margin of the parietals; and by the absence of the deep emargination which separates the superior maxillary from the tympanic bone in the fresh-water tortoises, and especially in the Podocnemys expansa. In general form, the skull of the present species of Sheppey Chielone resembles that of the Chelone mydas, BRONGN.: but it is relatively broader; the prefrontals (14) are CHELONIA. {1 less sloping, and the anterior part of the head is more vertically truncate. The orbits are relatively larger, and extend nearer to the tympanic cavity. The frontals (11) enter into the formation of the orbits in rather a larger proportion than in Cheloue mydas. In the Chelone caouanna* they are wholly excluded from the orbits. The trefoil shape of the occipital tubercle is well marked (fig. 4) ; the depression in the basioccipital, bounded by the angular pterygoid ridges, is as deep as in most true turtles (fig. 3); the lateral borders of the expanded parietals are united by a straight suture along a great proportion of their extent to the large postfrontals. These proportions are reversed in the Podocnemys eapansa, in which the similarly expanded plate of the parietals is chiefly united laterally with the squamosal and tympanic bones. In other fresh-water tortoises the parietal plate in question does not exist. The same evidence of the affinity of the Sheppey Chelonite in question to the marine turtles, is afforded by the base of the skull (fig. 3); the basioccipital (1) is deeply excavated ; the processes of the pterygoids (24), which extend to the tympanic pedicles, are hollowed out lengthwise: the palatal processes of the maxillary and palatine bones are continued backwards to the extent which characterises the existing Chelones; and the posterior or internal opening of the nasal passages, is, in a pro- portional degree, carried further back in the mouth. The lower opening of the zygomatic spaces is wider in the present Sheppey Chelonite, than in Podocnemys CHPUANSA. The external surface of the cranial bones in the fossil is roughened by small irregular ridges, depressions, and vascular foramina, which give it a wrinkled or shagreen-like character. The following are dimensions of the specimen described : Inches. Lines. Length of cranium from the occipital condyle : : “ 2 9 Breadth of cranium across the malars (26) —.. : : 5 2 7 Antero-posterior diameter of orbit é ; 5 5 ; 1 0 The lower jaw, which is preserved in the present fossil, likewise exhibits two characters of the marine turtles ; the dentary piece (32), é. g. forms a larger proportion of the lower jaw than in the land or fresh-water tortoises. The joint of the rami is completely obliterated at the symphysis, which is not longer or larger than in Che/one mydas. The species represented by this fossil, which is preserved in the British Museum, and by a very similar one in the Hunterian Collection, is selected for the first of the Eocene Chelonians to be described in the present Monograph, because it is one of the few with which the characters of the carapace and plastron can with certainty be associated with those of the cranium. * Ossem. Fossiles, tom. v, pt. ii, pl. xi, fig. 2. 12 FOSSIL REPTILIA OF THE LONDON CLAY. In the rich collection of Sheppey fossils, belonging to J. 8. Bowerbank, Esq. F.R.S. there is a beautiful Chelonite (Tab. II, figs. 1, 2) including the carapace, plastron, and the cranium, which is bent down upon the fore part of the plastron; and which, though mutilated, displays sufficient characters to establish its specific identity with the skull of the Chelone breviceps just described. Both the carapace and plastron present the same finely rugous surface externally as the cranium ; in which character we may perceive a slight indication of affinity with the genus Zrionye. The carapace (T. II, fig. 1) is long, narrow, ovate, widest at its anterior half, and tapering towards a point posteriorly; it is not regularly conver, but slopes away, like the roof of a house, from the median line (fig. 3), resembling, in this respect, and its general depression, the carapace of the turtle Chelone mydas. ‘There are preserved the nuchal plate (fig. 1, ch) with ten of the neural plates (~1—v10), only the eleventh and pygal plates being wanting. The eight pairs of costal plates (p/i—wpls) are also present, with sufficient of the narrower tooth-like extremities of the six anterior pairs of ribs, to determine the marine character of the fossil, which is indicated by its general form.* The nuchal plate (fig. 6, ch) is of a transversely oblong form, with the anterior margin gently concave. Its antero-posterior diameter, or length, is ten lines; its transverse diameter, or breadth, is two inches. The lateral margins are bounded by two lines meeting ata slight angle; to the anterior one, the first of the marginal plates, m1, is attached; the posterior line bounds part of the vacant interspace between the first costal plate (/1), and the anterior marginal plate. The presence of this plate would prove for the genus Chelone as against Trionyx, were the characters of the cranium, the impressions of the vertebral scutes, and the sternum wanting. The nuchal plate in the Himydes is hexagonal, and nearly as long as it is broad. The Chelonite from the tertiary beds near Brussels, figured by Cuvier,t has the nuchal plate of nearly the same form as the present specimen from Sheppey. The neural plates in the Chelone breviceps are as narrow as in the Chelones generally ; and as in the Brussels Chelonite above cited. The first neural plate (s1, fig. 1) is four-sided; the rest, to the eighth (ss), are hexagons of a more regular figure than in the existing Celones, and are articulated to more equal shares of the contiguous alternate costal plates (/1—p/s). The first costal plate (/1) is directed more outwards, does not incline backwards, as in recent Chelones, and its anterior angle is less truncated than in them. (See fig. :«l.qp2, 3:) The length of the second costal plate (p/2) is one inch, nine lines ; more than half of the narrow terminal extremity of the connate rib is preserved; the proportions of * In an Hmys with a carapace seven inches in length, the corresponding extremities of the ribs would have been united together by the laterally-extended ossification. + Ossemens Fossiles, tom. v, pt. 2, pl. xv, fig. 16. CHELONIA. 13 the remaining costal plates correspond with those of the Chelone mydas, and Chel. caouannda. The last pair of costal plates (p/s) articulates with the eighth, ninth, and tenth neural plates, but does not overlap or supersede any of them. Not any of the costal plates articulate with those of the opposite side, so as to interrupt the series of vertebral plates, as in the carapace of the Chelone caouanna (fig. 1, p. 3),as in Mr. Crowe’s Sheppey Chelonite, figured by Cuvier (tom. cit. pl. xv, fig. 12); and as is shown in the view of the concave surface of the Brussels species (tom. cit. pl. xv, fig. 16). The ninth neural plate (fig. 1, s9) is the narrowest, as in the Chelones, and as in the Brussels Chelonite, figured by Cuvier, in loc. cit. pl. xii, fig. 8, instead of being suddenly expanded, as in most Hmydes. The tenth neural plate (s10) expands to a breadth equal with its length; the eleventh and pygal plates, as already observed, are wanting in the fossil. The vertebral or median ends of the costal plates present a modification of form, corresponding with that of the interspaces of the neural plates to which they are articulated. Only the first pair (p/1) present that form which characterises all but the last pair in the existing Chelones, and in the Brussels Chelonite ; viz., a straight line with the posterior angle cut off; the rest being terminated by two nearly equal oblique lines, meeting at an open angle, as shown in Tab. II, fig. 1, p/2—p/7. This character would serve to distinguish the Chelone breviceps, if only a portion of the carapace, including the vertebral extremity of a rib, were preserved. The free extremities of the ribs are thicker in proportion to the costal plates, than in the Chelone caouanna, or the Chel. mydas ; and more resemble, in this respect, those of the Chel. wmbricata, the species characterised by the size and beauty of the horny scutes, commonly called “ tortoise-shell.” More or less complete impressions of the five horny vertebral scutes (vli—v5), and of four costal scutes on each side of the vertebral ones, show the forms and proportions of these characteristic parts, and especially of the median series, notwithstanding they were among the soluble and perishable elements of this ancient turtle of the Thames. The hexagonal vertebral scutes are characterised by the near equality of their sides, and the angle of about 100°, at which the two outer sides meet. The anterior border of the first vertebral scute, v', has crossed and impressed the nuchal plate, c/, near its anterior border; this scute has covered the rest of the nuchal plate, and more than half of the first neural plate. The second vertebral scute, v’, includes the rest of the first neural plate, the whole of the second, and almost the whole of the third neural plate. The third vertebral scute, v’, includes the hind border of the third neural plate, with the whole of the fourth and fifth neural plates. The fourth vertebral scute includes the sixth and seventh, and very nearly the whole of the eighth neural plates, and the outer angles of this scute terminate over the suture between the sixth and seventh costal plates. 14 FOSSIL REPTILIA OF THE LONDON CLAY. The plastron of the Chelone breviceps (Tab. IL, fig. 2), although more ossified than in existing Che/ones, yet presents all the essential characters of that genus. There is a central vacuity left between the hyosternals (4s) and hyposternals (ps); but these bones differ from those of the young mys in the long pointed processes which radiate from the two anterior angles of the hyosternals (4s), and the two posterior angles of the hyposternals (js). The xiphisternals (vs) have the slender elongated form, and oblique union by reciprocal gomphosis with the hyposternals (4s), which is characteristic of the genus Chelone. The posterior extremity of the right episternal (es) presents the equally characteristic, slender pointed form. With these proofs of the modification of the plastron of the present fossil according to the peculiar type of the marine Chelones, there is evidence, however, that it differs from the known existing species in the more extensive ossification of the component pieces; thus the pointed rays of bone extend from a greater proportion of the margins of the hyosternals and hyposternals; and the intervening margins do not present the straight line at right angles to the radiated processes. In the Chelone mydas, and Chel. caouanna (fig. 3, p. 4), for example, one half of the external margin of the hyosternal and hyposternal, where they are contiguous, are straight, and intervene between the radiated processes, which are developed from the remaining halves, while in the Chelone breviceps, about a sixth part only of the corresponding external margins are similarly free, and there form the bottom, not of an angular, but a semicircular interspace. The radiated processes from the inner margins of the hyosternals and hyposternals, are characterised in the Chelone breviceps by similar modifications, but their origin is rather less extensive ; they terminate in eight or nine rays, shorter, and with intervening angles more equal than in existing Chelones. 'The xiphisternal piece, as, receives in a notch the outermost ray or spine of the inner radiated process of the hyposternal, as in the Chelones, and is not joined by a transverse suture, as in the Hmydes, whether young or old. Subjoined are dimensions of the plastron of Mr. Bowerbank’s fossil : Inches. Lines. Shortest longitudinal diameter of hyosternal and hyposternal pieces 2 5 Transverse diameter of ditto 2 ; : ; 5 5 1 7 Total length of plastron : 5 : : 5 5 : 6 0 The bones of the scapular arch, especially the coracoid, Cuvier has shown to afford distinctive characters of the natural families of the Chelonia ; but the Eocene Chelonites described by Cuvier, did not yield him this opportunity of thus testing their affinities. In the Chelone breviceps here described, the left coracoid (52, fig. 2) is preserved in nearly its natural position; it is long, slender, symmetrical; cylindrical near its humeral CHELONIA. 15 extremity; flattened, and gradually expanded from its humeral third, to its sternal end, which is relatively somewhat broader than in the Chelone mydas and Chelone caouanna. Inch. Lines. Its lengthis . : : : : 1 6 Breadth of sternal end ; 5 : 0 7 The characters thus afforded by the cranium, carapace, plastron, and by one of the bones of the anterior extremity, prove the present Sheppey fossil to belong to a true sea turtle; and at the same time most clearly establish its distinction from the known existing species of Chelone. On account of the shortness of the skull, especially of the facial part and of that which intervenes between the orbit and ear, compared with the breadth of the skull across the mastoids, I have proposed to name this extinct species, Chelone breviceps.* By the characteristic shape of the median extremities of the costal plates of the carapace, I have been able to determine some fragmentary Chelonites which have afforded better ideas of the size of the species represented by Mr. Bowerbank’s more complete but immature specimen of Chelone breviceps. A portion of the carapace of the Chelone breviceps, including the fourth, fifth, sixth, and part of the third and seventh neural plates, with a considerable proportion of the third, fourth, fifth, and sixth costal plates, is preserved in the museum of Mr. Robertson, of Chatham. The characters of the rugous surface of these bones, and of the equal- sided angles by which the costal plates articulate with the neural plates, do both, and especially the latter, point out the species to which the present fragment belongs. It has formed part of an individual double the size of the specimen above described, and figured from Mr. Bowerbank’s collection, and therefore it had a carapace sixteen inches in length. Although the costal plates have been continued further along the ribs than in the younger example, the more complete state of the sixth rib, in Mr. Robertson’s specimen, shows that they retained their longitudinally-striated, tooth-hke extremities, which, in the sixth rib, is two thirds of an inch in length; the length of the expanded part being four inches, and its breadth one inch nine lines. The internally prominent part of the rib is much less developed than in Chelone planimentum, and Chelone crassicostata, afterwards to be described. The right hyosternals and hyposternals are present, and they likewise preserve the character of the Chel. breviceps in their rugous surface and minor breadth, as compared with those parts in the Chelone longiceps, the extinct species next to be described. Besides the specimens above described, on which the present extinct species of turtle * Proceedings of Geological Society, December 1, 1841, p. 570. Report on British Fossil Reptiles, Trans. Brit. Association, 1841, p. 178. 16 FOSSIL REPTILIA OF THE LONDON CLAY. has been established, remains of the Chelone breviceps are preserved in the Hunterian Museum, and in that of my esteemed friend and coadjutor, Professor Bell, $.R.S. I know no other locality of the species than that of Sheppey, in Kent. CHELONE LONGICEPS. Owen. Tab. III, IV, and V. Proceedings of Geological Society of London, December 1, 1841, p. 572. Report on British Fossil Reptilia, Trans. British Association, 1841, p. 177. The second species of Chelone, from the Eocene clay at Sheppey, which I originally recognised and defined by the fossil skull, Tab. III, differs more from those of existing Chelones by the regular tapering of that part into a prolonged pointed muzzle, than does the Chelone breviceps by its short and anteriorly-truncated cranium. The surface of the cranial bones is smoother than in the Chel. breviceps ; whilst their proportions and relations prove the marine character of the present fossil as strongly as in that species. The orbits (Tab. III, figs. 1 and 2, 0,) are large; the temporal fossee (ib. fig. 3, ¢,) are covered principally by the posterior frontals (fig. 2,12); and the osseous shield completed by the parietals (7), and mastoids (8), overhangs the tympanic (28), ex- occipital (2), and paroccipital (4) bones. The compressed spine (3) of the occiput is the only part that projects further backwards. The palatal and nasal regions of the skull afford further evidence of the affinities of the present Sheppey Chelonite to the true turtles. The bony palate (fig. 3) presents, in an exaggerated degree, the great extent from the intermaxillary bones to the posterior nasal aperture which characterises the genus Ohelone ; and it is not perforated, as in the soft turtles (Zrzonyx), by an anterior palatal foramen. The extent of the bony palate is relatively greater than in the Chelone mydas, and the trenchant alveolar ridge is less deep; the groove for the reception of that of the lower jaw is shallower than in the Chelone mydas, or the extinct Chel. breviceps, arising from the absence of the internal alveolar ridge, in which respect the Chel. longiceps resembles the Chel. caretta. The Chelone longiceps is distinguished from all known existing Chelones by the proximity of the palatal vomer (13, fig. 3), to the basisphenoid (5), and by the depth of the groove of the pterygoid bones (24), and in both these characters in a still greater degree from the Trionyxes; to which, however, it approaches in the elongated and pointed form of the muzzle, and the trenchant character of the alveolar margin of the jaws. The following are dimensions of the skull described : Inches. Lines. Length of the skull : : ; 5 ; : : 6 4 0 Breadth of ditto across the zygomat : : : : = 2 6 Antero-posterior diameter of orbit . ? Bi ‘ 3 F 1 2 CHELONTA. 17) In a second example of the skull of Chelone longiceps, two of the middle neural plates, and the corresponding costal plates of the right side, portions of vertebree, with the right xiphisternal piece, humerus and femur, are cemented together, and to the cranium by the petrified clay. (T. IV, fig. 1.) The neural plates (s2, s3) are flat and smooth; the entire one measures one inch two lines in length, and nine lines across its broad anterior part :—this receives the convex posterior extremity of the preceding plate in a corresponding notch. A small proportion, about one sixth, of the anterior part of .the external margin, joins the second costal plate (p/2); the remaining five sixths of the outer margin forms the suture for the vertebral end of the third costal plate (/3). In this respect, the Chel. longiceps resembles the existing Chelones ; and differs, as well as in the smooth and flattened surface of the vertebral plates, from the Chelone breviceps. The length of the third costal plate, in the fragmentary example here described, is three inches ; the impression of the commencement of the narrow portion, formed by the extremity of the coalesced rib, is preserved. The marginal indentations of the vertebral scutes are not half a line in breadth. The transverse impression between the first and second vertebral scute crosses the first neural plate, nine lines from its posterior extremity ; the second neural plate is free, as in other Chelones, from any impression, being wholly covered by the second vertebral scute. The expanded ribs are convex at the under part, slightly concave at the upper part in the direction of the axis of the shell; they slope very gently from the plane of the neural plates, about half an inch, for example, in an extent of three inches; thus indicating a very depressed form of carapace. The xiphisternal bone (as), like that of Chel. breviceps, is relatively broader than in the existing turtles, and both the internal and external margins of its posterior half are slightly toothed. A part of the notch by which it was attached to the hyposternal remains upon the broken anterior extremity of the bone. It measures one inch two lines across its broadest part; its length seems to have been three inches and a half. The humerus presents the usual characters of that of the Chelones ; its length is two inches three lines; its breadth across the large tuberosities ten limes. The radius and ulna extend in this Chelonite from beneath the carapace into the right orbit; the radius is one inch and a half in length; the ulna one inch, three lines in length ; portions of vertebre adhere also to the mass, the state of which indicates that the animal had been buried in the clay before the parts of the skeleton had been wholly disarticulated by putrefaction. A mass of Sheppey clay-stone supporting the ninth and tenth neural plates, and the expanded portions of the sixth, seventh, and eighth costal plates of the right side, exhibits the characters of the marine turtles in the great relative expansion of the 3 18 FOSSIL REPTILIA OF THE LONDON CLAY. tenth neural plate ; and the tooth-like continuation of the rib from the posterior angle of the eighth costal plate (pls, T. IV, fig. 2). These portions of the carapace, from their smooth surface, the impressions of the horny scutes, the form of the vertebral ends, and the concavity of the upper surface of the costal plates, evidently belong to the same species as the fossil last described. A similar mass of Sheppey clay-stone, in Mr. Lowe’s collection, supports a larger proportion of the hinder part of the carapace, including the sixth, seventh, eighth, ninth, and tenth neural plates, part of the fifth neural plate, more or less of the last four pairs of costal plates, with the impressions of the third and fourth ribs of the right side; the impression of apparently the whole of the free, slender, termination of the third rib is preserved, and also that of the fifth rib, confirming the generic characters indicated by the skull. The smooth outer surface of the bones of the carapace, the forms of the neural plates, and the concomitant modification of the commencement of the costal plates articulated therewith, concur to establish the specific distinction from the Chelone breviceps, and indicate the specimen to belong to the present species, Chelone longiceps. The seventh, eighth, and ninth neural plates progressively decrease in size; and the ninth presents a simple, quadrangular, oblong form ; the tenth neural plate suddenly expands, and has apparently a triangular form, but its posterior border is incomplete. The indications of the comparative flatness of the carapace of the Chelone longiceps, (in this respect, as in the elongated and pointed form of the skull, approaching the genus Zrionyx,) which were derived from an examination of the foregoing fragments, and particularly of the portion preserved with the crantum on which the species is founded, are fully confirmed by the almost entire carapace which, subsequently to the publication of my ‘Report on British Fossil Reptiles,’ where the present species is first noticed, I have had the opportunity of examining in the collection of Mr. Bowerbank. This carapace, as compared with that of the Chelone breviceps in the same collection, presents the following differences :—it is much broader and flatter. The neural plates are relatively broader; the lateral angle from which the intercostal suture is continued, is much nearer the anterior margin of the plate—the Chelone longiceps, in this respect, resembling the existing species of turtle (see fig. 1, p. 3). The costal plates are relatively longer ; they are slightly concave transversely to their axis on their upper surface, while in Chel. breviceps they are flat. The external surface of the whole carapace is smoother ; and although it is as depressed as in most turtles, it is more regularly convex; not sloping away by two nearly plane surfaces from the median longitudinal ridge of the carapace. The following minor differences may be noticed in the two Sheppey Chelonites : the nuchal plate of the Chel. longiceps (Tab. V, fig. 1, ch) is more convex at its middle part, and sends backwards a short emarginate process to join the first neural CHELONTIA. 19 plate (s1) ; in which it resembles the Chel. mydas. Both posterior angles of the first neural plates are produced, and truncate to articulate with the second pair of costal plates ; and the second neural plate is quadrangular. In a portion of another carapace of the Chelone longiceps the second neural plate (s2) is pentangular, the right anterior corner being produced, and truncate to join with the first costal plate of the right side ; the left posterior corner of the first neural plate (s1) being produced, and truncate, to articulate with the second costal plate of the left side. This structure I believe, however, to be an individual variety. But the characters of the species are exemplified in more constant modifications of the carapace. The succeeding neural plates to the seventh inclusive (s3—s7) are hexagonal, with the anterior lateral border much shorter than the posterior lateral border, as in Chelone mydas, and not of equal extent, as in Chelone breviceps ; they become more equal in the seventh and eighth neural plates, which also decrease in size; the ninth plate (s9) is very small, quadrangular, and oblong, as in Mr. Lowe’s fragment. Only a small portion of the tenth neural plate is preserved in Mr. Bowerbank’s beautiful specimen. The impressions of the horny scutes are deeper, and the lines which bound the sides of the vertebral scutes (vi—v4) meet at a much more open angle than in the Chel. breviceps, in which the vertebral scutes have the more regular hexagonal form of those of the Chel. mydas. ‘Their relations to the neural plates are nearly the same as in Chel. breviceps. The plastron (Tab. V, fig. 2) is more remarkable than that of the Chel. breviceps for the extent of its ossification ; the central cartilaginous space being reduced to an elliptical or subquadrangular fissure. The four large middle pieces hyosternals (hs) and /yposternals (ps), have their transverse extent relatively much greater as compared with their antero-posterior extent, than in the Chel. breviceps; and this might be expected, in conformity with the broad character of the bony cuirass indicated by the carapace. ‘The median margins of the /yosternals (4s) are developed in short toothed processes, along their anterior three fourths; the median margins of the Ayposternals (ps) have the same structure along nearly their whole extent ; the intermediate space between the smooth or edentate margins of the opposite bone is ten lines; the expanded end of the long coracoid (52) is seen projecting into this space. . The xiphisternals (vs) are relatively broader than in Chel. dbreviceps, or in any of the existing turtles; and are united together, or touch each other, by the toothed processes developed from the whole of their median margins. The entosternal piece is broad, flat on its under surface, and is likewise dentated at its sides. The outer surface of each half of the plastron inclines, as in the Chelone mydas, towards a submedian longitudinal ridge. The breadth of the plastron, in the specimen figured (fig. 2), along the median suture, uniting the hyosternals and hyposternals, is six inches: the narrowest antero- posterior diameter of the conjoined hyosternals and hyposternals is two inches nine lines. 20 FOSSIL REPTILIA OF THE LONDON CLAY. The breadth of the plastron, at the junction of the xiphisternals with the hyposternals, is two inches six lines. The posterior part of the cranium is preserved in Mr. Bowerbank’s specimen (fig. 1), withdrawn beneath the anterior part of the carapace ; the fracture shows the osseous shield covering the temporal fosse; and the pterygoids remain, exhibiting the deep groove that runs along their under part. It is most satisfactory to have found that the two distinct species of the genus Chelone, determined, in the first instance, by the skulls only, should thus have been confirmed by the subsequent comparison of their bony cuirasses ; and that the specific differences, manifested by the cuirasses, should be proved by good evidence to be characteristic of the two species founded on the skulls. Thus the portion of the skull preserved with the carapace first described (Tab. II, figs. 2 and 3), served to identify that fossil with the more perfect skull of the Chelone breviceps (Tab. I), by which the species was first indicated. And, again, the portion of the carapace adhering to the perfect skull of the Chelone longiceps (Tab. IV, fig. 1) equally served to connect with it the nearly complete osseous buckler (Tab. V, fig. 1), which, otherwise, from the very small fragment of the skull remaining attached to it, could only have been assigned conjecturally to the Chel. longiceps ; an approximation which would have been the more hazardous, since the Chelone breviceps and Chelone longiceps are not the only turtles which swam those ancient seas that received the enormous argillaceous deposits of which the Isle of Sheppey forms a part. CHELONE LATISCUTATA. Owen. Tab. VI. Proceedings of the Geological Society of London, December J, 1841, p. 574. Report on British Fossil Reptiles, Trans. British Association, 1841, p. 179. A considerable portion, measuring three inches in length, of the bony cuirass of a young turtle from Sheppey, including the first to the sixth neural plates (T. VI, fig. 1, s1—s6), with the corresponding pairs of costal plates (p/i—p/6), and the hyosternal (fig. 2, As) and hyposternal (ps) elements of the plastron, most resembles that of the Chelone longiceps in the form of the carapace, and especially in the great transverse extent of the above-named parts of the plastron: it differs, however, from the Chel. longiceps, and the other known fossil Chelonites, in the greater relative breadth of the vertebral scutes (v2, v3), which are nearly twice as broad as they are long. The central vacuity of the plastron is subcircular; and, as might be expected, from the apparent nonage of the specimen, is wider than in the Chel. longiceps ; but the toothed processes given off from the inner margin of both hyosternals and hyposternals are small, sub-equal, regular in their direction, and thus resemble those of the Chel. longiceps-~; the slender point of the episternal (s) is preserved in the interspace between CHELONIA. 2] the hyosternals. Both hyosternals (4s) and hyposternals (ps) are slightly bent upon a median longitudinal prominence of their under surfaces. The length of the third costal plate (/3) is one inch seven lines; its antero- posterior diameter or breadth, six lines: in the form of the vertebral extremities of the costal plates, and of the neural plates to which they are articulated, the present fossil resembles the Chel. longiceps ; but the fifth neural plate is more convex, and is crossed by the impression dividing the third vertebral scute (v3) from the fourth, which impression crosses the suture between the fifth and sixth neural plates in both Chelone longiceps and Chelone breviceps. Whether, in the progressive change of form, which the vertebral scutes may have undergone in the growth of this young turtle, as during the growth of the young loggerhead turtle (Chelone caouanna), by an increase of length, without corresponding increase of breadth, the impression between the third and forth vertebral scute, might also retrograde to the interval between the fifth and sixth neural plates, I am uncertain, having only had the opportunity of comparing the scutes of the young and old loggerhead turtles, not the skeletons. The change in the lateral angles of the vertebral scutes, resulting from the elongation of the scutes themselves, in the loggerhead, would be similar to that in the Chelone longiceps, as compared with the Chel. latiscutata, on the hypothesis that the latter is the young of the former ; but in my present uncertainty I prefer to indicate the specimen in question, by the definite name proposed in my original Memoir; its description as a distinct species being more likely to attract the attention of Collectors to similar specimens, and to enable them to identify such. Figure 3, T. VI, gives the degree of convexity of the carapace, and the double curve of the plastron produced by the prominence of the principal heemapophyses 4s and ys. The left scapular arch (51) is exposed in this view- CHELONE CONVEXA. Owen. Tab. VII. Proceedings of the Geological Society of London, December 1, 1841, p. 575. Report on British Fossil Reptiles, Trans. British Association, 1841, p. 178. The fourth species of Che/one, indicated by a nearly complete cuirass, from Sheppey, holds a somewhat intermediate position between the Chelone breviceps and the Chelone longiceps ; the carapace being narrower, and more convex than that of Chel. longiceps ; broader and with a more regular transverse curvature than in the Chelone breviceps. Although the specimen is equal in size to either of the two with which it is here compared, the costal plates hold an intermediate length, which shows that this character is not due to a difference depending upon age. The fossil in question includes the first to the eighth neural plate inclusive ; the first plate (s1) expands behind, and both posterior angles are truncated to articulate with the second costal plates (/2). The second neural plate (s2) is quadrate, half as long again as broad, and the second pair of costal plates articulate with this, as 22 FOSSIL REPTILIA OF THE LONDON CLAY. well as with the first and third plates, as in the Chel. longiceps (Tab. V, fig. 1). The tooth-like extremity of the connate rib is preserved on the right side. The fourth costal plate (p/4) is two inches four lines in length, nine lines in breadth ; the angle at which the expanded part contracts to the extremity of the connate rib is well shown on the right side. ‘The third to the eighth neural plates expand anteriorly, and have the anterior angles cut off to articulate with the costal plates in advance ; they diminish in size very gradually, and the antero-lateral borders, formed by the above-named truncated angles, do not increase in length as im the corresponding plates in the Chelone longiceps. The vertebral scutes (v2, v3, v4) resemble more in form those of the Chel. longiceps than of Chel. breviceps ; but, notwithstanding that the whole carapace is narrower than in Chel. longiceps, the vertebral scutes are broader ; and the lines which converge to the lateral angle have a more marked sigmoid curvature. Chel. convexa. Chel. longiceps. Inches. Lines Inches. Lines. The length of the second vertebral scute is 1 8 1 8 Breadth ; i 5 A ‘ ; 2 6 2 2 The two succeeding scutes (v3 and v4) more rapidly diminish in size than in either the Chel. breviceps or longiceps, and the transverse impression between the third and fourth vertebral scute crosses the lower third of the fifth neural plate, as in Chelone latiscutata. All the scutes have left deeper and rather wider impressions than in the preceding species. The second to the fifth costal plates inclusive, are more equal im length than in the existing Chelone mydas or Chel. caouvanna, and in this character the present species more resembles the Chel. imbricata. The distinction of the present from the previously described fossils, already manifested in the structure of the carapace and the form of the vertebral scutes, is more strikingly established in that of the plastron (Tab. VII, fig. 2), which, in its defective ossification, resembles the same part in the existing species of Che/one. All the bones, but especially the xiphisternals (vs), are more convex on their outer surface than in other turtles, recent or fossil. The central vacuity is greater than in any of the above-described fossil species. The internal rays of the hyosternals come off from the anterior half of their inner border, and are divided into two groups: the lower consisting of two short and strong teeth, projecting inwards towards the extremity of the entosternal (s); while the rest extend forwards along the inner side of episternals (es). The same character may be observed in the corresponding processes of the Ayposternals (ps), which are limited to the posterior half of their inner border. The external radiated process of the hyosternals (/s) arises from a larger proportion of the outer margin, than in the Chel. mydas ; but from a somewhat less proportion than in Chel. breviceps. CHELONTA. 23 The external process of the hyposternal (ps) is relatively much narrower than in the Chel. breviceps (T. Il, fig. 2), and, @ fortiori, than in Chel. longiceps (Tab. V, fig. 2). The straight transverse suture by which the hyosternals and hyposternals of the same side are joined together, is much shorter than in the other fossil Chelones ; and is similar in extent to that in Chel. mydas ; but the following differences present themselves in the plastron of the Chelone convexa, as compared with that of the Chelone mydas. The median margin of the hyosternals forms a gentle curve, not an angle: that of the hyposternals is likewise curved, but with a slight notch. The longitudinal ridge on the external surface is nearer the median margin of the /yosternals and hyposternals and is less marked than in the Chelone longiceps ; especially in the hyposternals, which are characterised by a smooth concavity in the middle of their outer surface. The suture between the /yosternals and hyposternals is nearer to the external, transverse, radiated process of the hyposternals. The median vacuity of the sternal apparatus is elliptical in the Chel. convera, but square in the Chel. mydas. The characteristic lanceolate form of the episternal bone (s) in the genus Che/one, is well seen in the present fossil. The entosternal element of the plastron is sub- circular, or lozenge-shaped ; and generally broader than it is long in the Emydians. The true marine character of the present Sheppey Chelonite, so well given in the carapace and plastron, is likewise satisfactorily shown in the small relative size of the entire femur (65) which is preserved on the left side, attached by the matrix to the left xiphisternal. It presents the usual form, and slight sigmoid flexure, characteristic of the Chelones ; it measures one inch in length. In an Himys of the same size, the femur, besides its greater bend, is one inch and a half in length. A Chelonian cranium from Sheppey, two inches five lines in length, in the museum of Professor Bell (T. VI, fig. 4), and a second of the same species from the same locality, two inches nine lines in length, in the museum of Fred. Dixon, Esq., F.G.S., of Worthing, belong to the same species, and differ from the cranium of the Chelone breviceps, in the more pointed form of the muzzle, and the less rugose character of the outer surface of the bones; they equally differ from the Chelone longiceps in the less produced, and less acute muzzle, and the more rugose surface of the bones. The parietals (7) are bounded anteriorly by a semicircular line, not by a semioval one, as in Chel. longiceps, or by an angular one, as in Chel. breviceps. The frontals (11) enter into the formation of the orbits, as in both the foregoing species. The orbits are subcircular, as in Chel. longiceps, not subrhomboidal with the angle rounded off, as in Chel. breviceps. The postfrontals (12) are large, and form a slight projection at the back part of the supraorbital ridge. The tympanic cavity is larger in proportion than in the Chelone longiceps. The palate is traversed by a deep median, longitudinal groove, between which and the shallower grooves on the inner sides of the alveolar borders, are two well-marked, diverging, longitudinal prominences. The 24 FOSSIL REPTILIA OF THE LONDON CLAY. bony palate is longer than in Chelone breviceps, shorter than in Chel. longiceps. The symphysis of the lower jaw (T. VII, fig. 3) is longer or deeper than in the Chelone breviceps, but is convex below from side to side, and not flattened as in the Chelone planimentum. All the specimens of Chelone convexa, which I have been able to determine, are from the London clay of Sheppey. CHELONE SUBCRISTATA. Owen. Tab. VIII. Proceedings of the Geological Society of London, December 1, 1841, p. 576. Report on British Fossil Reptiles, Trans. British Association, 1841, p. 179. The fifth species of Chelone from Sheppey, distinguishable by the characters of its carapace, approaches more nearly to the Chelone caouanna in the form of the vertebral scutes (vl—24), which are narrower in proportion to their length, than in any of the previously described species; but the Chelone subcristata is more conspicuously distinct by the form of the fifth and seventh neural plates (s5, s7), each of which supports a short, sharp, longitudinal crest; a similar crest is developed from the contiguous ends of the second and third neural plates (s2, 53); the middle and posterior part of the nuchal plate (c/) is raised into a convexity, as in the Chel. longiceps ; but not into a crest. The keeled structure of the above-cited neural plates is more marked than in the third and fifth neural plates of Chelone mydas, which are raised into a longitudinal ridge. The neural plates in the present carapace have the ordinary, narrow, elongated form of those in the true Chelones. The nuchal plate (ch) has the middle of its hinder border produced backwards, instead of being emarginate, as in the Chel. breviceps (T. II, fig. 1,cf). The first neural plate in the Chelone subcristata (T. VIII, s1) resembles that in the Chelone convexa, but is narrower in proportion to its length; the second (s2) is also quadrangular, as in Chel. convexa, but is narrower; the third to the seventh likewise differ from those in Chel. convexa only by being narrower; but the eighth and ninth neural plates are relatively smaller than in any of the before-described fossils, and resemble those of existing Chelones. The expanded plate is more elevated, and is bent down on each side, with the middle part forming an obtuse longitudinal ridge. A part of the contiguous portion of the first (p/1) and the second (p/2) costal plates are raised into a slight convex eminence on each side; the surface of the remaining pairs of ribs is flat in the axis of the body, but they are more convex transversely to that axis, and in the direction of their own length, than in the other Chelonites. The whole outer surface of the bones of the carapace is as smooth as in the Chel. longiceps and Chel. convexa. Length of carapace from the first to the eighth neural plate inclusive : Ch. subcristata. Ch. breviceps. Ch. longiceps. Ch. convexa. Inches Lines. Inches __ Lines. Inches. Lines. Inches. Lines. 7 4 5 6 5 9 5 8 CHELONIA. 25 The length of the present fossil carapace, to the tenth neural plate, inclusive, is nine inches. . The breadth between the ends of the third costal plates, in a straight line, is six inches six lines. The succeeding costal plates more gradually decrease in breadth, than in the Chel. longiceps and Chel. convexa ; and the entire carapace more resembles in form that of the Chel. mydas, and Chel. caowanna. The epidermal scutes are defined by deep impressions, and as wide, relatively, as in the Chel. mydas and Chel. convexa. 'The length of the second vertebral scute is two inches one line ; its breadth is two inches two lines ; the length of the fourth vertebral scute is two inches three lines; and its breadth one inch eleven lines, and, at its posterior margin, only nine lines. This scute is narrower than in Chel. caouanna, or any of the previously described fossil species; the outer angles are less produced than in the Chelone caouanna. Sufficient of the plastron is exposed in the present fossil to show by its narrow elongated xiphisternals (vs), and by the wide and deep notch in the outer margin of the conjoined hyosternals and hyposternals (/s and ps), that it belongs to the marine Chelones. 'The xiphisternals are articulated to the hyposternals by the usual notch or gomphosis; they are straighter and more approximated than in the Chel. mydas and Chel. caouanna. 'The external emargination of the plastron between the hyosternals and hyposternals, differs from that of the recent turtles in beimg semicircular, instead of angular; the Chel. subcristata approaching, in this respect, to the Chel. breviceps. The shortest antero-posterior diameter of the conjoined hyosternals and hyposternals is two inches seven lines. The length of the xiphisternal is two inches six lines; the breadth of both, across their middle part, is one inch three lines. The name proposed for this species indicates its chief distinguishing character, viz., the median interrupted carina of the carapace, which may be presumed to have been more conspicuous in the horny plates of the recent animal, than in the supporting bones of the petrified carapace. CHELONE PLANIMENTUM. Owen. Tab. IX and X. Proceedings of the Geological Society of London, December, 1841, p. 576. Report on British Fossil Reptiles, Trans. British Association, 1841, p. 178. Syn. Curetonr Harvicensis, Woodward (°). The skull of a large Chelone (T. TX) from the Eocene clay near Harwich, in Professor Sedgwick’s collection at Cambridge, resembles, in the pointed form of the muzzle, the Chel. longiceps of Sheppey; but differs in the greater convexity and breadth of the cranium (fig. 2); and the more abrupt declivity of its anterior contour (fig. 3), and from other Chelones by the broad expanse of the inferiorly-flattened symphysis menti (fig. 1). 4 26 FOSSIL REPTILIA OF THE LONDON CLAY. The osseous roof of the temporal fossz, and the share contributed to that roof by the postfrontals (T. IX, figs. 2 and 3, 12), distinguish the present, equally with the foregoing Chelonites, from the Lmys (Podocnemys) eapansa, and, a fortiori, from other genera and species of the fresh-water families (Ymydide and Trionicide). In the oblique position of the orbits (fig. 3, 0), and the diminished breadth of the interorbital space (fig. 2), the present Chelonite, however, approaches nearer to Zrionyax and /mys than do the previously-described species. But the sides of the face converge more rapidly towards the muzzle. Its most marked and characteristic difference from all existing Chelones is shown by the greater antero-posterior extent, breadth, and flatness of the under part of the symphysis of the lower jaw, whence the specific name here given to the species. The posterior border of the symphysis is defined by a regular semicircular curve, and the rami of the jaw have completely coalesced. Since at present there is no means of identifying the well-marked species, of which the skull is here described, with the Chelonite figured in the frontispiece to Woodward's ‘Synoptical Table of British Organic Remains,’ and alluded to, without additional description or characters, as the Chelonia Harvicensis, in the additions to Mr. Gray’s ‘Synopsis Reptilium’ (p. 78, 1831); and since the extensive deposit of Eocene clay along the coast of Essex, like that at the mouth of the Thames, contains the relics of more than one species of ancient British turtles,* I prefer indicating the one here established by a name having reference to its peculiarly distinguishing character, rather than to associate arbitrarily the skull, which gives the true specific distinction, with the ill-defined carapace to which the vague name of Harvicensis has been applied; more especially as the fossil carapace to which the present skull more probably belongs, from the circumstance under which it was discovered, also presents well- marked, and readily-recognisable specific characters. This carapace (T. X) is also contained in the museum of Professor Sedgwick, and is understood to have formed part of the same individual turtle as the skull (T. IX) on which the species, Chel. planimentum, was founded. In general form this carapace differs from that of the existing Chelones, in being less contracted and pointed posteriorly than in the Chelone mydas and Chel caouanna, and more contracted posteriorly than in the Chel. zmébricata. In the proportion which the pleurapophyses (true ribs), bear to the superimposed costal plates, (p/a—s) it resembles Chelone mydas, and Chelone caouanna, more than it does the Chel. imbricata. But the pleurapophyses are more prominent and distinct from the costal plates throughout their entire length, than in the Chel. mydas or Chel. caouwanna, and present an obtuse angular ridge towards the cavity of the abdomen. The five posterior pairs of ribs of the carapace (p/4—yp/s) are preserved, with part * Sir C. Lyell alludes to the Chelonites of Harwich in his ‘ Elements of Geology :’ ‘‘ This formation is well seen in the neighbouring cliffs of Harwich, where the nodules contain many marine shells, and sometimes the bones of Turtles.” (Vol. ii, p. 337.) CHELONIA. 27 of the first three on the left side, and one of the coracoids (52) showing the rather sudden and considerable expansion of its sternal or mesial half. The interval between the free extremities of most of the ribs, is about equal to twice and a half the breadth of each extremity; but the interval between the seventh (pl7) and eighth (pls) rib, measured, like the others, at the terminal border of the costal plates, is equal to thrice the breadth of the free part of the seventh rib. In this respect the Chelone planimentum resembles the Chel. mydas more than it does the Chelone caouanna, in which the interval between the free extremities of the seventh and eighth ribs is less than that between the sixth and seventh. The length of the costal plate of the fourth rib is twice that of the eighth rib, as in the Chelone caouanna ; in Chel. mydas it is more than twice as long; in Chel. imbricata it is only one third longer. The marginal pieces in the Chelone planimentum seem to have been narrow or slender in proportion to their length. The following admeasurements show that, in the large proportionate size of the head, the Chelone planimentum corresponds with the existing turtles : Inches. Lines. Length of the cranium . : ; ; : 5 . : 5 6 Depth of ditto . 5 : 4 ; ; : : 3 4 0 Breadth of ditto . 7 : , ; : ; ; : 5 0 Length of the carapace . : : : 6 : : Sunes 6 Greatest breadth of ditto 5 : : ; : : s 13 0 Tab. IX and X satisfactorily illustrate the characteristic forms and proportions of the unique specimen in the Cambridge Museum ; the carapace is figured of half the natural size. CHELONE CRASSICOSTATA. Owen. Tab. XI and XII. Trstupo Prana. Kénig. ‘ Icones Sectiles,’ Pl. XVI, fig. 192? That the extinct species of Eocene turtles attained larger dimensions than those given above, is proved by a fossil skull from the Harwich clay, in the collection of Professor Bell, which gives the following dimensions : G Inches. Lines. Total length of the cranium . : : : . : 8 0 Its greatest breadth F : : . 6 0 The antero-posterior extent of the symphysis menti . 3 0 The vertical diameter of the orbit . 1 9 do. do. of the nostri . 0 9 This skull differs from that of the Chelone planimentum in the minor depth of the maxillary bone below the orbit (compare T. IX, fig. 3, with T. XI, fig. 2, 21), in the more acute and attenuated muzzle; but especially in the minor breadth and the different configuration of the posterior margin of the symphysis of the lower jaw (compare T. IX, 28 FOSSIL REPTILIA OF THE LONDON CLAY. fig. 1, with T. XI, fig. 3). With regard to the comparative anatomy of the bones of the skull, and the pattern of the scutation of the upper surface of the cranium, I regret that the state of the specimen in Professor Bell’s collection does not permit the deduction of other distinctive characters which such parts of the cranial organization so satisfactorily afford. A great proportion of the osseous parietes is wanting ; but the cast in the hard matrix of the wide lateral cavities (12, 12), which were over-arched by the expanded postfrontal and parietal bones, indicates the prominence of the postfrontals at the upper and outer angle of the orbits. The orbits (07) appear to have been more ovate and less circular than in the Chelone planimentum ; and the sides of the orbital part of the skull do not converge so rapidly towards the muzzle, but meet at a more acute angle. That a second species of turtle, distinct from the Chelone planimentum, has left its remains in the Harwich clay, is very decisively demonstrated by the almost complete carapace in the British Museum, the inner surface of which is represented, on the scale of six inches to a foot, in T. XII. This carapace, both by its general contour, by the relative length of the costal plates to one another, and by their relative breadth to the adherent pleurapophyses beneath, more resembles the carapace of the Chelone imbricata than that of the other known existing species of turtle; and, as the peculiar characters of the Chelone imbricata are exaggerated, it differs in a proportional degree from the Chelone planimentum. These characters are seen in the great breadth of the pro- minent, inferior part of the ribs, and of the free extremity of the rib (p/1—p/s), as compared with the total breadth of the costal plate. The intervals between the free extremities, where the expanded plate terminates, are not equal to the breadth of the proper ribs ; in the Chelone imbricata they very slightly exceed the breadth of the free ends of the ribs. This character in the fossil, by which it is so markedly distinguished from the Chelone planimentum, and most other species, has suggested the name Chelone crassi- costata, or thick-ribbed turtle, which is proposed for the present species. The last pair of ribs of the carapace (T. XII, p/s) are remarkably short and thick, and are curved backwards on each side the broad terminal neural plates which they almost touch. In this character the Chel. crassicostata resembles the Chel. imbricata, and — differs from the Chel. caouanna (fig. 2, p. 3), and from Chel. mydas. The subequality of length of the costal plates is another character by which the Chel. crassicostata resembles the Chel. imbricata, and differs from the Chel. mydas, the Chel. caouanna, as well as from the Chel. planimentum. In T. XII, as in the other figures, ch is the nuchal plate, p/i the first rib of the carapace (the second free pleurapophysis or vertebral rib), p/2 to pla the remaining ribs of the carapace and costal plates ; s9, s10, and py are the terminal neural plates and pygal plate, which, like the nuchal plate, are developed in the substance of the integument, without becoming attached to the subjacent spinous processes of the vertebree. The debris of the neural arches of the intermediate eight vertebrae of the CHELONIA. 29 carapace are preserved in the interspaces of the beginnings of the ribs and costal plates in this beautiful Chelonite. It forms part of the Fossil Collection in the British Museum. A carapace of a smaller individual of Chelone crassicostata, from the Harwich coast, with the character of the broad and inwardly-prominent ribs strongly marked, is likewise preserved in the choice collection of my esteemed friend Professor Bell. One of the hyosternal bones, inclosed in the same nodule of clay, testifies to the partial ossification of the plastron in this species by its coarsely-dentated border ; and, at the same time, shows a specific peculiarity by the convexity of that surface which was turned towards the cavity of the thoracic-abdominal case. On the moiety of the nodule containing the carapace and exposing its under surface, the slender rudimental rib of the proper first dorsal vertebrze is preserved, in connexion with the first expanded rib of the carapace. Besides the specimen of Chelone crassicostata from Harwich, figured in T. XII, there is a mutilated carapace of a young Chelone, from the same locality, in the British Museum. This specimen exhibits the inner side of the carapace, with the heads, and part of the expanded bodies, of four pairs of ribs, which indicate its specific agreement with the foregoing specimen, and demonstrate unequivocally its title to rank with the marine turtles. It is figured in Mr. Keenig’s ‘ cones Sectiles’ (pl. xvi, fig. 192), under the name of Zestudo plana. A rare Chelonite from the hard Eocene clay apparently of Harwich, in the collection of my friend Frederick Dixon, Esq., F.G.S., of Worthing, shows the impressions from the under surface of the carapace, and also an instructive part of the under surface of the plastron itself. (T. XIII.) The proportions and degree of convexity of the under surface of the costal plates of the carapace (p/, p/) correspond with those parts in the Chelone erassicostata. The remains of the plastron include a great portion of the left hyosternal (As), left hyposternal (ys), and left xiphisternal (vs) ; the latter is articulated to the hyposternal by a notch, receiving a toothed process, and, reciprocally, near the upper part of a long oblique harmonia, between the outer border of the hinder angle of the hyposternal and the inner border of the upper half of the xiphisternal. The hyosternal is concave lengthwise, and is convex across on its under surface ; the transverse linear impression, dividing the pectoral and abdominal scutes, crosses near its posterior border. The degree of concavity of the outer surface of this bone corresponds with the convexity of the upper and inner surface of the same bone in the specimen of the Chelone crassicostata from Harwich, in the Museum of Professor Bell; and it concurs with the characters of the costal plates in proving the present Chelonite to be of the same species. Impressions of the toothed mesial margin of the right hyosternal remain, and part of the toothed margin of the left hyposternal. 30 FOSSIL REPTILIA OF THE LONDON CLAY. The right coracoid (52) is exposed by the removal of the right hyosternal ; it differs in form from that preserved in the large specimen of Chelone planimentum, in Professor Sedgwick’s Museum, in expanding less suddenly at its sternal end, as compared with the coracoid of the Chelone mydas, or with that of the Chelone caouanna, which is somewhat broader than in the Chel. mydas; the coracoid of the Chel. crassicostata agrees with that of the Chel. planimentum in the greater degree of its expansion. At the anterior fractured surface of Mr. Dixon’s Chelonite, the long and slender columnar or rib-like scapula, is shown, extending from the under part of the head of the second costal rib downwards and outwards, for an extent of two inches, and then sending its acromial or clavicular prolongation at the usual open angle downwards and inwards to rest upon the episternal. The proportions of these parts of the scapular arch are quite those which characterise the genus Chelone, but they do not supply such ods of specific distinction as the coracoid element does. CHELONE DECLIVIS. Owen. Tab. XIV. The extinct turtle represented by this specimen, and indicated by the above term, bears the same relation to the Chelone convexa, which the Chelone longiceps* does to the Chelone latiscutata ;¢ that is, it has the same general characters of the petrified parts of the carapace, but differs in the narrower proportions of the vertebral scutes (vli—vw4), and the more open angle at which their two lateral borders meet ;_ the vertebral angles of the costal scutes being correspondingly less acute. The specimen is from the Eocene deposits of Bognor, Sussex, and is preserved in - the collection of Frederick Dixon, Esq. It consists of the seven anterior neural plates, and the corresponding seven pairs of costal plates (T. XIV), those of the right side having been broken away from their attachments to the neural plates, and bent upon the rest of the carapace at an acute angle with some slight separation of the sutures of the costal plates (fig. 2). The neural plates correspond in general form with those of the Chelone conveza, the hind ones being rather broader; the first (s1) is crossed at its middle part by the impression dividing the first (v1) from the second (v2) vertebral scute ; the second neural plate (s2) is an oblong four-sided one, with both ends of equal breadth. The third neural plate, s3, resumes the hexagonal figure with the broadest end, and two shortest sides at the fore part; and is crossed in its lower half by the impression dividing the second, v2, from the third vertebral scute, v3. The fifth neural plate (s5) is crossed by the next transverse impression nearer its lower border. The sixth and seventh neural plates retain the same form and proportions as in the Chelone convexa, except a somewhat * Proceedings of the Geological Society of London, December 1, 1841, p. 572. + Ibid., p. 574. CHELONTA. 31 greater breadth, and have not their antero-lateral borders increased in length, as in the Chelone longiceps. The declination of the ribs from the neural plates, gives a greater degree of steepness to the sides of the carapace than in the Chelone convera, and the impressions of the scutes have equal depth and breadth. The chief difference indicative of specific distinctions, lies in the form of those impressions; and the question is, whether, in the progress of growth which makes the longitudinal extent of two of the vertebral scutes in one specimen nearly equal to three, in another, so great a change could be effected in their shape as is shown in the specimen of Chelone convera ; in which it will be seen that the second vertebral scute (T. VII, v2), though more than one third shorter than in Chel. declivis (T. XIV, v2), is of the same breadth as that in the larger specimen, and that the rest differ in the same remarkable degree. CHELONE TRIGONICEPS. Owen. More than one of the old tertiary turtles (Chelone) are remarkable for the longitudinal extent or depth of the symphysis of the lower jaw. The turtles from the Eocene clay at Harwich have this character so strongly developed and the under surface of the symphysis so flattened, especially in one of the species, as to have suggested the “ nomen triviale” planimentum for it. The Chelone longiceps, if we may judge by the length of the upper jaw and bony palate, must have had a corresponding extent of the symphysis of the under jaw; and we may infer the same peculiarity from the straight alveolar borders of the maxillaries and their acute convergence towards the premaxillary bones in an allied species, Chelone trigoniceps, which I have described and figured in the Appendix to Mr. Dixon’s work on the ‘Fossils of Sussex,’ from a specimen which is in the collection of G. A. Coombe, Esq., and which was obtained from the Eocene clay at Bracklesham. Amongst the Chelonites which Mr. Dixon has obtained from the same formation and locality, are portions of the fore part of the lower jaw of four individuals of the genus Chelone, all exhibiting the characters of the pointed form and great depth of the symphysis. One of these specimens agrees so closely in size and shape with the fore part of the upper jaw of the Chelone trigoniceps—fits, in fact, so exactly within the alveolar border, and so closely resembles that specimen in texture and colour, that, coming from the same formation and locality, and being obtained by the same collectors, I strongly suspect it to belong to the same species of Chelone, if not to the same individual. The known recent Chelones differ among themselves in the shape and extent of the bony symphysis of the lower jaw. Both the Chelone imbricata, and Chelone caouanna have this part deeper and more pointed than the Chel. mydas, but neither species has 32 FOSSIL REPTILIA OF THE LONDON CLAY. the symphysis so depressed or so slightly convex below as it is in the Bracklesham Chelones. These also differ amongst themselves in this respect. The symphysis which I have referred to the Chelone trigoniceps, is the broadest and flattest ; at its back part it shows a deep and broad genio-hyoid groove ; this is reduced to atransversely oblong foramen in Chelone mydas. The second species from Bracklesham, is indicated by the maxillary symphysis, the sides of which meet at a more acute angle, and it is narrower in proportion to its length, is more convex below, and more concave above, with the alveolar borders a little more raised, and the middle line less raised than in Chelone trigoniceps. In this respect it is intermediate between the Chelone imbricata, where the upper surface of the symphysis is more concave, and the Chelone caowanna, where it is flatter than in the Chelone trigoniceps. The fossil symphysis under notice, has also a smooth, transverse, genio-hyoid groove at its back part. It accords so closely in form with the end of the upper jaw of the Chelone longiceps, from Sheppey, that I refer it provisionally to that species. Two other specimens of the symphysis of the lower jaw, of rather larger size, appear to belong to the same species as that referred to the Chel. longiceps, by the characters of the concavity of the upper surface, the convexity of the lower surface, and the degree of convergence of the sides or borders of the symphysis. The larger of the two shows the genio-hyoid groove, and the nearly vertical outer side of the jaw, opposite the back part of the symphysis, and this shows no impression of the smooth fossa receiving the insertion of the biting muscles, whereas, in the Chelone trigoniceps, fig. 11, that fossa extends to the same transverse line or parallel with the back part of the symphysis. The very rare and interesting Chelonite in Mr. Coombe’s museum, was the first portion of the cranium of a reptile of this order that I had seen from the Eocene deposits at Bracklesham. It includes the bones forming the roof of the mouth, with portions of the bony nostrils and orbits, and the tympanic pedicles. The extremity of the upper jaw is broken off, but the straight converging alveolar borders clearly indicate the muzzle to have been pointed, as in the Chelone longiceps of Sheppey; and the muzzle being shorter, the form of the skull has more nearly approached that of a right-angled triangle. The whole cranium is broader and shorter, and the tympanic pedicles wider apart. The middle line of the palate developes a some what stronger ridge; the orbits were relatively larger and advanced near to the muzzle: the malar bones are more protuberant behind the orbits, and their external surface inclines inwards as it descends from behind and below the orbit, to form the lower border of the zygoma, which it does not do in the Chelone longiceps. The upper surface of the fossil shows the palatines rising to form the vomer at the middle line, and the two small subcircular vacuities (occupied by membrane in the CHELONIA. 33 recent skull) between the palatines, prefrontals, and maxillaries; the anterior border of the temporal fossa, formed by the malar and pterygoid, is entire on one side, and shows that that vacuity was as broad as it is long. The olfactory excavations in the maxillaries are deep. The articular surface of the tympanitic pedicles closely accords with those of recent Chelones. The very regular triangular form of the skull indicated by this fragment, has induced me to propose the name of Chelone trigoniceps for the species. CHELONE CUNEICEPS. Owen. Tab. XV. One of the most complete and instructive crania of the fossil turtles of our Eocene deposits is the subject of T. XV, the opportunity of describing and figuring which has been kindly afforded me by J. Toulmin Smith, Esq., F.G.S., of whose cabinet it forms part, and by whose skilful manipulation its variously configurated exterior has been ‘disencumbered of the hard adherent clay. From the Chelone breviceps this specimen differs by its more prolonged and pointed muzzle; by the more sudden and sloping declivity of the prefrontal part of the cranium (fig. 1, 14); by the minor degree of rugosity of the surface of the bones ; and by the different disposition of the superincumbent horny scutella, which is indicated by their impressions. In the general arrangement of these impressions it accords better with the cranium of the Chelone longiceps ; but differs in the greater breadth of the skull as compared with its length; im the mimor extent of the bony palate (fig. 3, 20, 21), the more advanced position of the posterior nostrils, and the greater length of the pterygoids (24). From the Chelone conveva it differs, in the greater relative breadth and flatness of the frontal bones, and of the whole interorbital platform (fig. 2, 11), in the downward slope of that part of the cranial profile, and in the more prominent convexities of the palatal processes of the maxillaries. From the Chelone planimentum it differs also, by the broader prefrontal part of the interorbital space, as compared with the transverse diameter of the back part of the skull; by the minor degree in which the frontal enters into the formation of the upper rim of the orbits; by the minor depth of the suborbital part of the maxillary and malar bones, and by a very different arrangement of the supracranial horny scutella. The basi-occipital (T. XV, figs. 3 and 4) is remarkable for the strong development of the tubercles for the insertion of the strong “ recti capitis antici,” and for the depth of the median groove between them; the semicircular fossa im front of these processes is bounded by a well-developed basi-sphenoidal ridge (5), the curve of which is deeper than in Chel. longiceps, but shallower than in Chel. breviceps. In the Chel. caowanna, in which the basi-occipital tuberosities are better developed than in the Chel. imbricata or Chel. mydas, they are bounded anteriorly by an angular or chevron-shaped ridge of the basi-sphenoid. The exoccipitals (2) form the usual share of the trilobate occipital 5 34 FOSSIL REPTILIA OF THE LONDON CLAY. condyle characteristic of the Chelonia. The paroccipitals (4) project backwards to a little beyond the posterior plane of the condyle, indicating an affinity to the Zrionycida. The inferior surface of the part of the tympanic to which they unite is concave. The parietals (fig. 2, 7) form together a large semielliptic, almost flattened, platform, relatively broader than m Chel. mydas, not convex, as in Chel. caowanna; not in- dented by the mastoids, as in the Chel. longiceps, and not forming an angle between the frontals and postfrontals, as in the Chel. breviceps. The frontals (11) together form a pentagon, with the longest margin joining the parietals, the next in length con- verging to a point between the prefrontals, and the shortest borders joining the post- frontals. The postfrontals (12) and prefrontals (14) almost meet above the orbits, and exclude the frontals from entermg into the formation of its superior border. The Chel. mydas comes nearest to the Chel. cuneiceps in this particular ; whilst in the Chel. imbricata the frontals enter as largely into the formation of the upper border of the orbit as they do in the Chel. breviceps, Chel. longiceps, and Chel. convezxa. The precise form of the termination of the prefrontonasals, the maxillaries, and premaxillaries cannot be determined in the present specimen ; fortunately, the fracture of the anterior extremity of the skull has not extended to that of the bony palate. If this be bounded by a transverse line behind, drawn across the anterior border of the temporal fossz, the space included forms a right-angled triangle, and includes the whole of the posterior nostrils. In the Chel. longiceps the similarly defined space has the base shorter than the converging sides, and the posterior nasal aperture is behind the transverse line. The bony palate, also, of Chel. cuneiceps, instead of being pretty uniformly concave and even, as in Chel. longiceps and Chel. caouanna, is raised on each side between the middle line and the marginal alveolar plate into two convexities, as in Chel. mydas and Chel. imbricata; but the most prominent part of the palatal convexities (figs. 3 and 4, 21) is obtuse in Chel. cuneiceps, not sharp or angular, as in Chel. mydas and Chel. imbricata. The palatal part of the vomer (13) forms the median longitudinal groove dividing the convexities, which are formed by the palatal processes of the maxillary bones, The small part of the alveolar border of the maxillary which is entire terminates in a sharp edge, extending about four and a half lines below the level of the palate. The ridge of the palatines, which forms the anterior boundary of the posterior nostril, is not produced or bent below the level of the bony palate, as in Chel. caouanna, and as it is, although in a minor degree, in Chel. mydas ; and there is not that concavity between it and the oblique palatal tuberosity which exists in the Chel. mydas and Chel. imbricata. The pterygoids are more deeply (semicircularly) emarginate laterally than in any of the existing species of Chelones, and they are shorter in proportion to their breadth ; they bound internally the lower apertures of the temporal fossze, which are broader than they are long; in all the existing Chelones the opposite proportions prevail, CHELONIA. yf 39 and in Chel. imbricata especially the homologous apertures are twice as long as they are broad. The pterygoids, in the Chel. cuneiceps, develope a sharp ridge along their median suture; and short but well-defined processes at their anterior and outer angles. The channel or concavity upon the under part of the diverging portion of the pterygoid conducts obliquely into the temporal fossee in the Chel. mydas; in Chel. cuneiceps it leads directly forwards upon the under surface of the anterior part of the pterygoids exclusively, as in the Chel. imbricata and Chel. caouanna. In the Chel. mydas the malar approaches the mastoid very closely, and sometimes touches it by the posterior angle, thus separating the squamosal from the postfrontal ; the extent of the union between the squamosal and postfrontal is also shorter in the Chel. caouanna than in the Chel. imbricata. In the extent of that union (between 12 and 27) the Chel. cuneiceps resembles the Chel. imbricata, as do likewise the Chel. breviceps and Chel. longiceps. But the Chel. cuneiceps differs from all the recent species in the form of tle squamosal (27), which is bent upon itself, forming a slightly curved linear eminence, where the lower and smoother part of the bone is bent, and, as it were, pressed inwards towards the tympanic (28), against which it abuts. This modification is natural, not the effect of accidental pressure upon the fossil. The lower border of the malar (26), which intervenes between the maxillary and squamosal, is sharp but convex, as in Chel. caowanna, not concave as in Chel. mydas, nor nearly straight, as in Chel. imbricata. But the concave curve of the inferior margin of the squamosal (27) most resembles that in Chel. imbricata. The antero-posterior extent of the mastoid (8) is less proportionally than in any of the recent Celones, and it forms a smaller share of the upper border of the large meatus auditorius. The articular part of the tympanic descends below the squamosal further than in the recent turtles ; and its articular surface is more convex at its outer half, and more concave at its inner half; Chel. imbricata makes the nearest approach to the fossil in this respect. In the Chel. mydas and Chel. caouanna the articular surface is nearly flat. As the supracranial scutella have left unusually deep and well-marked impressions on this fossil skull, I have reserved their description, and the comparison of their different forms and proportions in the several fossil species, to this place. Three scutella occupy the median line of the upper surface of the cranium in the present species of Chelone, which, from the absence of any impression along the frontal and sagittal sutures, appear to have been single and symmetrical. The anterior and smallest answers to the “ frontal” scute (/r) ; the next in size and position to the “ sincipital” scute (sy); the hindmost and largest answers to the “ occipital” scute (0c), which is usually divided, and forms a pair in existing Chelones. The frontal scute is long, narrow, hexagonal, broadest across the antero-lateral angles, from which the- impressions extend outwards to the supraorbital margin, which divide the “ fronto-nasal” scute from the “ supraorbital” scute (04). The sincipital scute is bounded on each side by a sigmoid curve, and both before 36 FOSSIL REPTILIA OF THE LONDON CLAY. and behind by an entering angle; it is broadest behind, and from the middle of the lateral border proceeds the transverse impression towards the back part of the orbit, which divides the “ supraorbital” scute (04) from the “ parietal” scute (ya). The occipital scute is bounded laterally by straight lines, which slightly diverge as they extend back- wards: there is no trace of an interoccipital scute. The parietal (pa) scuté is the largest; impressions of five of its borders are preserved in the present fossil: the two exterior ones meet at an obtuse angle, a little above the middle of the meatus auditorius externus ; the antero-external border uniting with the postorbital scute (yo); the postero-external border with the external occipital scute (eo). In the Chelone breviceps (T. I) the frontal scute is relatively larger than in the Chelone cuneiceps, and is nearly as broad as long. ‘The sincipital scute is bounded laterally by two straight lines meeting at a very open angle, from which the transverse impression extends outwards between the supraorbital and parietal scutes. The straight lines bounding the sides of the occipital scute diverge from each other as they extend backwards more than they do in the Chelone cuneiceps. In the Chelone longiceps (T. Il) a still more different pattern of the supracranial scuta- tion is presented. The occipital scutes (oc) are separated by an intervening interoccipital scute (70). The lateral borders of the sincipital scute are each bounded by three lines and two angles; the antero-lateral and postero-lateral angles being curved with the concavity outwards; and the transverse impression dividing the supraorbital scute (06) from the parietal scute (ya), proceeds from the middle of the intervening straight border of the parietal. The frontal scute (/r) is long and narrow, broadest behind, with its lateral borders gradually converging to a point anteriorly; the impression dividing the supraorbital (04) from the frontonasal scute (fn) proceeds from the middle of that lateral border. Neither the division between the frontal and sincipital, nor that between the sincipital and interoccipital scutes are well marked. The Chelone conveza (T. VI, fig. 4), like the Chelone longiceps, has an interoccipital scute (70), and the sincipital scute (sy) has its sides bounded by three lines, of which the posterior one is curved with its concavity towards the occipital scute (0c), and so directed as to appear to form part of the posterior rather than the lateral border ; the other two lines completing the lateral border and converging forwards, are divided or defined by a slight angle, from which the transverse impression proceeds outwards, which divides the supraorbital (04) from the parietal (ya) scutes. The frontal scute (fr) is a small hexagon, relatively wider than in Chel. longiceps or Chel. cuneiceps. The impression dividing the supraorbital (04) from the frontonasal (/”) scutes proceeds from the angle between the lateral and anterior sides of the frontal scute. The Chelone planimentum (T. 1X) is peculiar, and differs from all the foregoing species by the forward extension of the occipital scutes which join the supraorbital scutes, and thus divide the sincipital scute (sy) from the parietal scute (ya); the sincipital scute CHELONTA. 37 is correspondingly encroached upon, as it were, and narrowed, its broadest part being nearer the anterior end, at the angle between its two straight lateral borders, from which angle the impression extends outwards that divides the occipital from the supra- orbital scute. The frontal scute (/r) is small and narrow, and the large supraorbital scutes meet in front of it at the middle line. They appear to be divided from the orbits by the encroachment of palpebral scutes (p/) upon the supraorbitary border. There appears to have been an interoccipital scute in the Chel. planimentum, as in the Chel. longiceps and Chel. convewa. Amongst existing Chelones the interoccipital scute is constant only in the Chel. caouanna—the loggerhead of Catesby and Brown; but the sincipital scute in this species is vastly larger in proportion than in any of the fossils above described ; and it is further distinguished by the peculiar division of the supraorbital and parietal scutes. In the hawks-bill turtle (Chel. imbricata), the supracranial scutes leave as well- marked éndentations upon the bones of the cranium as are seen in most of the fossil turtles, but the supraorbital scute is proportionably larger than in any of these, and the proportions and forms of all the other scutes are different. There are, also, two nasal scutes divided by a transverse groove from the frontonasals, which groove I have not yet met with in the corresponding part of any of the fossil Chelonian crania. The skull of the Chelone cuneiceps, here described, is from the London clay of Sheppy. CHELONE SUBCARINATA. Jel/. Tab. VIII Z. The resemblance of this species to Chelone subcristata (p. 24, T. VIII) is so con- siderable, that it has not been without some hesitation that I have ventured to describe itas distinct. There are, however, certain characters by which it may be distinguished, and those of sufficient importance to be considered as specific. On comparing it with recent species, and even with most of the fossil ones from the same locality, there is a remarkable evenness in the arch of the carapace, which, with the exception of a slight carina on some of the posterior neural plates, to be hereafter mentioned, forms nearly a perfect arc of a circle, from the extremity of the costal plate of the one side to that of the other, without that flattening of the side which is seen in most other species. The nuchal plate (T. VIILA, fig. 1, ch) has the posterior margin arched, and there is a short median process which goes to join the first neural plate (si), in which respect it agrees with Chel. longiceps and with Chel. subcristata. This process is emarginate, to receive a slight triangular projection of the anterior margin of that plate. The first neural plate (s1) forms a parallelogram, the sides not being interrupted by any costal suture ; the posterior suture of the first costal plate (y/1) extending to the second neural plate (s2). In this circumstance it differs from Chel. subcristata, longiceps, and convera, and agrees with Chel. breviceps. This, however, may possibly be a variable character here, as 38 FOSSIL REPTILIA OF THE LONDON CLAY. it is in Chel. longiceps ; im one specimen of which, now before us, Professor Owen found that the articulation in question was to the anterior part of the second, instead of the posterior part of the first, neural plate ; in other words, that the first neural] plate was the isolated one instead of the second. The remaining neural plates are hexagonal, becoming almost regularly shorter to the eighth ; the lateral angles meeting the costal sutures being nearly at the same distance from the anterior margin in each, and in no one at all approaching a regular equilateral hexagon, as in many of the neural plates in Chel. breviceps. ‘The first three, and the anterior half of the fourth neural plates are flat; but on the posterior half of the fourth commences a low carina, which becomes highest on the posterior half of the sixth (sé), and anterior half of the seventh (s7). It thus differs from Chel. subcristata, mm which there is a distinct. short, sharp, longi- ~ tudinal crest (si) on the fifth and seventh neural plates, “ and a similar crest is developed on the contiguous ends of the second and third neural plates.” The ninth and tenth neural plates are wanting in the only specimen I have seen of the Chel. subcaginata. The first costal plate is flat (p/i), but the remaining ones, to the seventh inclusive, are slightly hollowed along the middle, being raised towards the anterior and posterior margins, where they are articulated to the contiguous ones. The whole surface of the bones of the carapace is less smooth than in most other fossil species, and conspicuously less so than in Chel. subcristata. In describing the forms of the vertebral scutes, (~1—v4), and of the costal ones as depending upon them, it is necessary, in order to arrive at any satisfactory comparison between these parts in different species, to bear in mind that a great change takes place in their outline during the growth of the animal; and that a vertebral scute, which, in a younger individual, has the middle of its outer margin exceedingly extended, so as to form a very acute angle, where the lateral margin of the costal scute joins it, and thus rendering it twice as broad as it is long, may in more advanced age have that angle very open, and having increased greatly in length, and scarcely at all in breadth from angle to angle, the length becomes greater than the breadth. Allowing, however, for this fact, there are doubtless considerable variations in this respect according to the different species, which are permanent and well marked. The first vertebral scute (v1) in the present species is quadrilateral, broader anteriorly ; the second and third (v2, v3) hexagonal, with the outer margins slightly waved, somewhat broader in the middle at the angles than at the anterior and posterior margins, the comparative breadth at that part being rather greater than in the corresponding scutes of Chel. subcristata, and much less so than in Chel. convexa, Chel. breviceps, or Chel. longiceps. The fourth vertebral scute (v4) is also hexagonal, but the portion posterior to the lateral angles is narrowed and produced backwards. The last of the series is fan-shaped. The outline of the costal scutes follows of course that of the vertebral ones. The plastron, in the specimen from which this description is taken (PI. VIII, A, fig. 2), is more perfect than in that of almost any other fossil Chelonian I have seen. It CHELONIA. 39 agrees in its general form with that of Ciel. subcristata, but is less extensive, as regards its bony surface, than in Chel. longiceps or even than in Chel. breviceps. The entosternal bone (s) is somewhat wedge-shaped, with the anterior margin triangular, and a short winged process on each side of the anterior third of the bone extending outwards and backwards. The posterior extremity of the bore, and the winged processes are dentate. The episternals (es) are aliform, tending backwards and outwards, and inclosing between them the head of the entosternal (s), and the anterior processes of the hyosternal bones (4s). The latter have the anterior processes extending forwards on each side of the entosternal, approximating at their extremity the aliform processes of that bone. The median or internal processes nearly meet on the median line, and the den- tations are deep but slender ; each hyposternal (ps) unites similarly with its fellow, and the posterior process extends backwards, in a long, narrow. triangular piece, uniting with the xiphisternal (as), which latter forms a very elongated rhomb, the breadth of which is scarcely one fourth of its length, which in the present specimen is no less than two inches six lines. This form, with the elongation and narrowness of the posterior process of the hyposternal, gives to the hinder portion of the plastron in this species a narrower and more elongated outline than we find in almost any other; an approach to which is, however, indicated in the imperfect specimen of Chel. subcristata figured in Plate VIII. The external notch, between the external process of the hyosternal and hyposternal, is deep and rounded. The central interspace is nearly quadrate, and about half as long again as it is broad. Inches. Lines. Length of the carapace as far as it is preserved : ? 9 5 Breadth of ditto from the extremity of the third costal plate on one side to that on the other . . ; : ; : 7 4 Ditto, following the convexity of the carapace . - . : 9 3 Length of plastron from the anterior margin of the episternal to the extremity of the xiphisternal . : : 5 8 4 Breadth of ditto across the hyosternals_ . . ; 2 : ze 0 The only specimen of this species which I have seen is from Sheppy, and is in the fine collection of J. S. Bowerbank, Esq., F.R.S. TOR SUPPLEMENTAL REMARKS ON THE TURTLES FROM THE LONDON CLAY AT HARWICH. In the progress of the works now carried on in a part of the Harwich cliffs, with a view to the acquisition of the remains of the animal tissues and bone-earth which form the nodules that are ground up and used as manure, many remains of the Chelonian reptiles which formerly frequented the seas from which those Eocene tertiary strata have been deposited have been discovered. Mr. Colchester, of Little Oakley, Essex, who carries on large works of this kind for the “ Fossil Guano,” as it is termed, has transmitted to me a number of the nodules in question. The most intelligible and instructive of these I have marked from 1 to 10 consecutively, and shall notice them here in the same order. No. 1. Chelone planimentum. This is the half of an oval nodule of petrified clay, 20 inches in Jength, by 17 inches in breadth, exposing an irregular group of disarticulated bones of the carapace and other parts of the skeleton. The species is determined by a fragment of one of the costal plates with the connate rib. The plate measures 25 inches in breadth, the rib 8 lines, and forms the usual partial prominence from the even surface of the under part of the costal plate. Almost the whole of the very broad but short nuchal plate is recognisable: it measures 6 inches in transverse diameter, and only 13 inch in antero-posterior diameter. Part of the hyosternal bones, and the impression of the humerus are recognisable. No. 2 is the half of a nodule, 20 inches in length and 17 inches in breadth, exposing part of the plastron, and some other bones of the skeleton of the Chel. plani- mentum. It shows well the natural form of the under and outer part of the hyposternal bone, which is much more deeply excavated than in the Chel. crassicostata ; the lower portion of the bone is narrower in proportion to its length, and the xiphisternals are also in proportion longer and narrower than in that species. No. 3. Chelone planimentum. The half of an oval nodule, 17 inches in length and 13 inches in breadth. The fractured side exposing a cast of the inner surface of the carapace, which measures in length from the nuchal to the tenth neural plate inclusive 133 inches ; and in breadth, across the third pair of costal plates from one end of the projecting rib to that of the opposite side, 11 inches. The anterior contour of the CHELONIA. Al carapace is well shown in this nodule, the marginal plates which join the nuchal plate being preserved. The free extremity of the rib attached to the third costal plate projects 1 inch 9 lines from that plate, and measures 7 lines in breadth, where it becomes free ; the breadth of the plate bemg nearly 2 inches. ‘The transverse curve of the carapace is shown by this specimen to be much less than in the Chel. crassicostata. No. 4. Chel. planimentum. 'The nodule shows partly a cast of the outer surface of the carapace, with part of the carapace itself. The outer angles of the third and fourth vertebral scutes are here seen with the inner angle of the third costal scute. The outer angles of the vertebral scutes are more prominent than in Chel. declivis, Chel. subcristata, Chel. subcarinata, Chel. convexa, or Chel. longiceps ; they resemble most those in Chel. breviceps. The breadth of the third costal scute is 4 inches. ‘The characteristic angular ridge, formed by the narrow connate rib, where it projects from the lower surface of the costal plate, is well shown in this specimen. No. 5. A nodule showing a cast of the under surface of the carapace seen from above, apparently of the Chel. planimentum. No. 6. A nodule, 10 inches long ‘by 9 inches broad, showing a still more imperfect cast of the under surface of the carapace, of apparently a younger specimen of the Chel. planimentum. No. 7. A fragment of a nodule showing the outer dentated extremity of the left hyosternal of the Chel. planimentum. No. 8. A portion of a nodule, with part of the carapace of the Chel. plani- mentum, showing the second to the seventh neural plates inclusive, and portions of the second to the seventh costal plates of the right side, with more or less of their bony substance broken away, exposing their coarse fibrous character, the fibres diverging on each side from the subjacent rib, as they extend obliquely towards the periphery of the carapace. The third neural plate is 2 inches 3 lines in length and 1 inch in breadth ; it is crossed at its middle part by a moderately broad and deep channel, indicating the junction of the second with the third vertebral scute. The third neural plate is hexagonal; the two shortest sides being formed by the truncation of the contiguous angles of the second costal plates bending down a little to articulate with them. The fourth neural plate is 2 inches 6 lines in length, and | inch 4 lines across the broadest part. The anterior surface is concave, the posterior convex ; the two longest sides converge towards the posterior surface, and are straight. The fifth and sixth neural plates progressively decrease in length, without a proportionate decrease in breadth. The breadth of the fourth costal plate is 2 inches 3 lines at its peripheral extremity: its length is 6 inches; the rib projects 2 inches beyond it. The upper 6 42 FOSSIL REPTILIA OF THE LONDON CLAY. surface of the neural and costal plates is so minutely fibrous or striated as to seem at first sight almost smooth. The upper surface of the costal plate seems naturally to be slightly concave in the direction of the axis of the carapace, but not so much as in Chel. crassicostata, and the rib is much bent lengthwise. No. 9. Chelone crassicostata (T. XIILA). This instructive specimen is contained in a subspherical nodule, 13 inches long by 12 inches broad, exposing a large proportion of the outer surface of the carapace, with more than one half of the circle formed by the marginal plates (mw7—py). The carapace has been fractured, and the ribs of the left side dislocated and pressed down below those of the right. The third (/3) to the eighth (pls) costal plates inclusive are present on the left side; the fifth to the eighth on the right side, and the neural plates from the fourth to the pygal plate (py) inclusive. The fourth, fifth, and sixth neural plates are hexagonal, with the anterolateral sides shortest, and chiefly remarkable for their great breadth in proportion to their length. The seventh and eighth are small, and more regularly hexagonal. The ninth is a broad sub- crescentic plate, with the broad concave side backwards, and the space between this and the pygal plate is filled up by an equally broad but pentagonal neural plate. The length of the nimth and tenth neural plates, with the pygal plate inclusive, is 2 inches 9 lines. The pygal plate is subquadrangular and broadest behind, where it is slightly emarginate. ‘The length of the fourth to the eighth neural plate inclusive is 3 inches 8 lines. The upper surface of the bones of the carapace is almost smooth. That of the costal plates is chiefly remarkable for its concavity transversely, or in the direction of the axis of the carapace, which is to a greater degree than in the Chel. subcristata or Chel. longiceps ; the les of the sutural union of these plates with each other forming so many ridges across the sides of the carapace. The degree of curvature or convexity in the direction of the length of the costal plate is much greater than in the Chel. planimentum. The length of the third costal plate is 33 inches, its breadth at the outer extremity, 1 inch 4 lines; the breadth of the rib where it projects beyond it is 9 lines. The margin of the plate attached to that rib is 1 inch 4 lines in length, and 8 inches in breadth. The margin of the plates gradually increases in breadth towards the posterior part of the carapace, the one joining the pygal plate being 1 inch 2 linesin breadth. The general form of the carapace of the Chel. crassicostata is shown by the present specimen to have been that of a full oval, with a gently festooned border, not pointed behind. No. 10. Chelone crassicostata (T. XIILB.) A still more remarkable example of this species was kindly transmitted to me by the Rev. 8. N. Bull, M.A., of Harwich, of which a figure is given in T. XIIIZ. When it first came into my hands it was an unpromising semioval nodule, 10 inches in length by 7 inches in breadth, presenting on its convex surface portions of the posterior neural and costal plates, with their external surface entire; but no trace of plastron on the flattened side. The degree of convexity formed by the costal plates equalled that of the CHELONTA. 43 most dome-shaped tortoise. The flatter surface of the nodule was slightly convex, which I thought might arise from a layer of petrified clay adhering to the plastron. A portion of the cranium was indicated at the produced angle of the nodule. To ascertain whether this remarkable degree of convexity of the carapace, both lengthwise and transversely, was natural, I had the matrix carefully removed, with the permission of the owner of the specimen, and the same was done on the opposite side, with a view to expose the plastron. Instead of finding a plane plastron where it was expected, in its natural horizontal position, it was found to have been crushed inwards, as _repre- sented in fig. 2, by the pressure of a hard petrified mass as big as a paving-stone, which had been forced in upon this part of the body of the turtle whilst in a decom- posing state; and when finally lodged in the clay, the carapace and plastron, as they became dislocated, had become more or less moulded upon it ; and thus was produced the convexity which originally attracted my attention. In the breadth of the connate rib, as compared with that of the costal plate, in the extent of the free extremity of the rib, in the degree of concavity of the upper surface of the costal plate and the curvature lengthwise, the distinctive characters of the Chel. crassicostata are well shown. The same characters are likewise presented by the parts of the plastron, as in the breadth of the xiphisternals (vs), the curvature of the hyosternal (4s), and the form of the coracoid. The two scapul, with the connate acromial clavicles, are preserved, with the head of one of the humeri. A part of the basis cranii, showing the broad diverging pterygoid, with their characteristically-channeled inferior surface, is shown in fig. 2; these grooves are not so deep, however, as in Chel. longiceps, but are more like those in Chel. cuneiceps. I beg to record my obligations to Mr. Bowerbank for the suggestion, and to Mr. Bull for his ready response to it, to which I owe the opportunity of examining this specimen of the thick-ribbed turtle of the Harwich cliffs. A fossil mandible of a Chelonian, in the collection of the Marchioness of Hastings (figured, of the natural size, in T. XIX J, figs. 1 and 2), most resembles that part in the genus Chelone by its general form and proportions, and especially by the configura- tion of the biting and grinding surface of the jaw (fig. 2). The symphysis is confluent; convex in both directions below ; longer than in the Chel. mydas and the Chel. breviceps of Sheppy (T. I, fig. 3, 32); but not so long as in the turtles from Harwich (T. IX, fig. 1, and T. XI, fig. 3) and Bracklesham, or as in the Chelone longiceps of Sheppy. The rami diverge more from each other than in the lower jaw of the Che/. convewva (T. VII, fig. 3) of Sheppy. A ridge, commencing at the fore part of the upper surface of the symphysis, passes backwards, and divides the two ridges, diverging and circumscribing with the outer sharp margins of the jaw an elliptical concave space on each side; the space between the diverging ridges is raised and rough: this part has been fractured. In the 7/vonyz, of which genus so many fine examples have been met with at Hordwell, the upper part 4A FOSSIL REPTILIA OF THE LONDON CLAY. of the symphysis presents an uniform concavity ; and this part of the jaw is narrower and more produced. I have not yet seen the mandible of any Emydian or land- tortoise resembling the present fossil so closely as some of the marine species above cited. A large species of Hmys has, however, left its remains in the same deposits at Hordwell as the Zvionyces next to be described. A retrospect of the facts above detailed, relative to the fossil Chelonians of the genus Chelone, or marine family of the order, leads to conclusions of much greater interest than the previous opinions respecting the Chelonites of the London clay could have suggested. Whilst these fossils were supposed to have belonged to a fresh-water genus, the difference between the present fauna and that of the Hocene period, in reference to the Chelonian order, was not very great; since the Himys or Cistuda Europea still abounds on the continent after which it is named, and livesslong in our own island in suitable localities. But the case assumes a very different aspect when we come to the conviction that the majority of the Eocene Chelonites belong to the true marine genus Chie/one; and that the number of species of these extinct turtles already obtained from so limited a space as the Isle of Sheppy, exceeds that of the species of Chelone now known to exist throughout the globe. Notwithstanding the assiduous search of naturalists, and the attractions to the com- mercial voyager which the shell and the flesh of the turtles offer, all the tropical seas of the world have hitherto yielded no more than five* well-defined species of Chelone ; and of these only two, as the Chel. mydas and Chel. caouanna, are known to frequent the same locality. It is obvious, therefore, that the ancient ocean of the Eocene epoch was much less sparingly inhabited by turtles; and that these presented a greater variety of specific modifications than are known in the seas of the warmer latitudes of the present day. The indications which the English eocene turtles, in conjunction with other organic remains from the same formation, afford of the warmer climate of the latitude in which they lived, as compared with that which prevails there in the present day, accord with those which all the organic remains of the oldest tertiary deposits have hitherto yielded in reference to this interesting point. That abundance of food must have been produced under such influences cannot, of course, be doubted; and we may infer that, to some of the extinct species, which, like the Chel. longiceps and Chel. planimentum, exhibit either a form of head well adapted for penetrating the soil, or with modifications that indicate an affinity to the Zrionyces, was assigned the task of checking the undue increase of the now extinct crocodiles and gavials of the same epoch and locality, by devouring their eggs or their young ; becoming probably, in return, themselves an occasional prey to the older individuals of the same carnivorous Saurians. * Mr. Gray, for example, includes the Chelone virgata and Chelone maculosa of Dumeril and Bibron as varieties of the Chelone mydas. CHELONTIA. AB Family—F.vviatia. Genus—TRIONYX. Tue Chelonian Reptiles called “Soft Tortoises,” forming the genus Zrionyx of Geoffroy St. Hilaire,* and the family Mwialia seu Potamites of MM. Duméril and Bibron,t resemble those of the genus Chelone (family Marina seu Thalassites, Dum. and Bibr.) in the extremity of the vertebral rib, or pleurapophysis, projecting freely from below the end of the connate costal plate,{ and in having the plastron incom- pletely ossified; but they are characterised by the still more incomplete ossification of the margin of the carapace, which retains much of its primitive soft, cartilaginous state ; and they are further distinguished by the reduced number of the toes—three on each foot—which are armed with claws, the other two toes serving to support a swimming web ; the name of the genus has reference to this peculiarity. The head is depressed, elongated, and, in the recent animal, the nostrils are pro- longed into a short tube, terminated by a small fleshy appendage like an elephant’s proboscis. The outer surface of the dermal bones of the carapace, and of the cor- responding parts of the plastron, is variously sculptured, usually by smuous grooves and rugosities, as if wormeaten; and to such a degree in some species, as to give the parts a tuberculate character. The cuticle is soft and flexible, not developed into scutes ; and there are accordingly no impressions like those that indicate the presence of the “‘ tortoise-shell” plates in the skeleton of the existing turtles and in the petrified plastrons and carapaces of the extinct species of the marine family. “Hitherto,” write the meritorious authors of the elaborate ‘ Erpételogie Générale,’ one has not observed any species of this family (Potamites) in our European rivers ; all those which have been described, and of which the habitat is known, have come from the streams, rivers, or great fresh-water lakes of the warmer regions of the globe.” (Tom. ii, p. 469.) The beautifully-preserved evidences of the species about to be described, which have chiefly been obtained by the Marchioness of Hastings from one limited locality, attest the abundance of the Zvionyces in the fresh-waters of our latitudes during the Eocene period of geology. The characters by which MM. Wagler and Duméril have divided the species of * Annales du Muséum d’ Histoire Naturelle, tom. xiy. + Erpétologie Genérale, 8vo, tom. ii, p. 461. t This character is well exemplified in the Marchioness of Hastings’s unique and beautiful specimen of the Trionyx rivosus, T, XVIILA. 46 FOSSIL REPTILIA OF THE LONDON CLAY. Trionyx, Geoffr., into two genera, are not such as can be decisively recognised in the fossil carapace. A difference of convexity of that part by which the “ Cryptopodes”’ are said to differ from the Gymnopodes, is not one that the comparative anatomist and paleontologist would recognise as valid for the distinction proposed. Upon the whole, the fossil specimens in which that character can be compared, agree rather with the Gymuopodes of Dum. and Bibr., but witha range of diversity which is exemplified by Tab. XVIL4, and XVII. So much of the plastron as I have been able to compare, agrees likewise with the bones of that part in the Gymnopodes, but, in the absence of more certain characters, and with doubts as to the necessity or desirableness of the subdivision proposed for the recent species, I shall retain the name Zyionyx for all the fossils that manifest, in their petrified remains, the characters of the Geoffroyan genus. In the second part of my ‘Report on British Fossil Reptiles’ I showed that certain fossils of the Wealden formation and of the Caithness slate (new red sandstone) had been referred erroneously to the genus Zrionyz, and that the only unequivocal remains of that genus which had been seen by me at that period (1841) were from Eocene deposits at Sheppy, Bracklesham, and the Isle of Wight, in which latter locality they were associated, as in the Paris basin, with remains of the Axoplotherium and Paleotherium. ‘ I have since had the opportunity of examining fossil specimens of Z7zonyx from other localities, but always, however, from formations of the Eocene period, and I shall commence their description with one of the most perfect and beautiful examples of these Chelonites, which was obtained by the Marchioness of Hastings from the Eocene sand of the Hordwell Chiff, Hants. TRIONYX HENRIcI. Owen. Tab. XVI. Report of the Seventeenth Meeting of the British Association, 1847, p. 65. Although the characteristics of the genus are readily recognisable in fossil fragments of the carapace and plastron, from their comparative flatness and the sculpturing of the outer surface, the species of 7rionye are with difficulty determinable, if at all, from such specimens ; and it is usually. necessary to have a considerable part of the carapace, in order to ascertain its composition, contour, and degree of convexity. Some species, indeed, e. g. Zrionyex rivosus (T. XVIILA), Zrionye marginatus (T. X1X*), together with the Zrionyx spinosus* and Trionyx sulcatus of Kutorga, would seem to be characterised by particular patterns of the irregular surface of the bones of the carapace, which character, therefore, a fragment may suffice to manifest; but this is not the case with the ordinary rugose and vermiculate species. Cuvier accordingly * This is quite a distinct species from the Trionywx spiniferus of Lesueur. CHELONIA. AT admits, with respect to the portions of Zronyr found abundantly in the gypsum of the environs of Paris, associated with the Palzotheres, Anoplotheres, and other extinct animals of the Kocene epoch, that he could find nothing in those fragments to authorize him to fix their specific characters.* The compilers of the labours of paleontologists have, as usual, been affected by no such scruples, and have not hesitated to assume a knowledge, which Cuvier did not feel himself entitled to claim, viz. that of the fact of the specific distinction of the Zrionyx of the Montmartre quarries: but I do not find that they have added anything to its history except the name of Zri. Parisiensis. It is probable, from the analogy of our own Eocene deposits, that more than one species of Zrionyx may have left its remains in the Parisian localities of the corresponding geological formation. The fossil remains of Zrionye from the tertiary deposits of the Gironde,t Lot-et- Garonne,t Montpellier, and Avary, were not sufficiently characteristic to permit the great anatomist and founder of Paleontology to infer more than the existence of the particular genus of fresh-water Chelonia in question in those formations. The only specimen of fossil Zrzonyz in which Cuvier recognised characters distinguishing it from the known existing species, is that which M. Bourdet first described§ under the name of Zrionya Maunoir, from the Eocene quarries at Aix. Cuvier has given reduced views of a large proportion of its carapace and half its plastron in the ‘Ossemens Fossiles,’ tom. v, pt. ii, Pl. XV, figs. 1 and 2. This description and the figure of the carapace serve to elucidate by comparison the characters of the more perfect specimen of Z?ionyx here described from the Eocene of Hordwell. In the first place, the contour and proportions of the entire carapace of the Tri. Henrict differ from those of the Zi. Maunoir. The carapace of the 77. Henrici, which is formed, as usual, by the neural plates (s1, s2, &c.) and eight pairs of costal plates (y/iI—s8), measures 10 inches 8 lines in length, and 11 inches 2 lines in breadth, in a straight line across the third (/3) costal plate, where it is widest. In Zr. Maunoir, the neural plates (plaques vertébrales) rise a little above the plane of the carapace, as in the Zi. ferox (Tri. carinatus, Geoffr.||) : in the Tri. Henrici there is no trace of this carinate structure ; the neural plates are flat, and on a level with the broad costal plates articulated with them; in which characters it resembles the Zi. gangeticus, Cuv., and Tri. javanicus, Cuv. The first costal plate (/i) is broader than it is long in Zr. Maunoir ; in Tre. Henrict its breadth is little more than half its length, and decreases as it recedes from * «Mais je n’ai rien trouvé dans ses débris qui m’autorisat 4 en fixer les caractéres spécifiques.” (Ossemens Fossiles, tom. v, pt. ii, p. 223.) + Cuvier, tom. cit., pp. 225, 227. t The skull of the Trionyzx from this locality showed a slightly different profile from that of any of the existing species. § Bulletin de la Société Philomathique, 1821. || Annales du Muséum, tom. xiv, pl. 4, 1809. A8 FOSSIL REPTILIA OF THE LONDON CLAY. the neural plate. The second costal plate, on the contrary, is broader at its lateral than at its mesial end in 777. Henrici, whilst its breadth is equal at both ends in the figure given by Cuvier of the Zz. Maunoir. The thickness of the costal plates, in proportion to their breadth, is shown in T. XIX4, figs. 4 and 5; the degree of projection of the connate rib from the inner surface of the costal plate is given in figure 6. The peripheral border of the carapace is not grooved in this species, as in the Tri. circumsulcatus, fig. 3. The degree of transverse convexity of the carapace of the Zi. Henrici is the same as that of the Zi. Zyyptiacus, and as that attributed to the Zri. Maunoir.* The nuchal plate is wanting in Lady Hastings’s specimen; the one which is figuredin T. XVI, fig. 3, is from the same locality at Hordwell, but does not belong to the carapace, fig. 1, although it has probably belonged to one of the same species, from the contour of its hinder border. The first neural plate (s1) does not project beyond the adjoiming anterior borders of the first costal plates (p/1) as it does in Zt. subplanus, Tri. ferox, and Tri. gavanicus ; nor do those borders, as they recede from the neural plate, curve forwards beyond it, as in 7rt. gavanicust and Tri. coromandelicus.t The anterior border of Zi. Henrict is slightly concave and gently undulated, as in the Zi. Aigyptiacus, and is also rough and sutural, showing that the anterior azygos or nuchal plate (“piece impaire,” Cuv.) had been immediately articulated with it, as it is in Zi. Aygyptiacus.§ The fossil specimen of the nuchal plate, figured in T. XVI, fig. 3, shows, by the sutural structure of its posterior border, that it articulated with the anterior sutural border of the carapace to which it belonged, and which, as already remarked, belonged probably to the species 777. Henrici, though not to the individual the carapace of which is figured in T. XVI, fig. 1. The neural plate (71) is longer in proportion to its breadth, and the corresponding costal plates (p/1) are narrower at their extremities than in Zr7. yyptiacus. The second costal plates (72) are broader at their extremities than in 77. gyptiacus ; they resemble those in 77. subplanus.|| The first four neural plates in Zi. Henrici slightly expand posteriorly, and have their posterior angles cut off; the fifth (75) is a narrow plate with entire angles; the sixth (76) is expanded anteriorly, and has its anterior angles cut off; the seventh (77) has also its anterior angles cut off, but is rounded behind, and, as it were, obliterated by the extension of ossification from the costal plates into the dermal cartilage above * «Sa convexité transversale est telle, que la fléche de l’arc est moindre du cinquiéme de la corde.” (Cuvier, Ossemens Fossiles, tom. v, pt. 2, p. 223.) + Annales du Muséum, tom. xiv, pl. 3, a. t Ibid., pl. 5, fig. 1. § Ibid., pl. 2, A, a. || Ibid., pl. 5, fig. 2. CHELONIA. 49 the neural spines. The eighth neural plate is wholly obliterated or superseded by a similar encroachment and union of the eighth pair of costal plates (p/s). Almost the same modification is represented by Geoffroy in the carapace of the 7ri. Ayyptiacus ;* but the general proportions of the carapace of the Zz. Henrici are more like those in the Zi. subplanus, in which the eighth neural plate exists in the interspace of the eighth pair of costal plates, as it does likewise in Zr?. Mannoir. All the exterior surface of the expanded parts of the neural spines and ribs is roughened or sculptured with a moderately fine vermicular pattern, the undulatory grooves having a tendency to a concentric arrangement at the peripheral surface of the carapace, and in general passing uninterruptedly from one costal plate to another: the pattern is effaced from about one third of an inch of the border of the carapace, which presents a surface like that of a coarsely-woven cloth. The extreme border is rather suddenly bevelled or rounded off from above downwards, and is thinner than the border of the costal plates that articulates with the neural plates. The natural extent of the ordinary narrow extremities of the ribs cannot be determined from the present specimen of the Ziv. Henrict ; they form the usual slight relief along the middle of the smooth under surface of the connate costal plates; and do not subside at any part of their course to the level of the under or inner surface of the plate. T. XVI, fig. 1, shows the upper surface of the carapace of the Zi. Henrict, half the natural size. Fig. 2, in outline below, gives the curve and degree of transverse convexity across the middle of the carapace. Fig. 3, the nuchal plate of apparently the same species of Z’rionyz, half the natural size. T. XIX, fig. 4, shows the outside view of the third costal plate, right side, natural size; fig. 5, sutural border of the same plate, showing its thickness and the degree of curvature ; fig. 6, the peripheral border of the same plate with the connate rib. All these specimens were discovered by the Marchioness of Hastings in the Eocene sand at Hordwell, and are preserved in her ladyship’s Museum at Efford House, near Lymington, Hampshire. The species is dedicated to her ladyship’s husband, Captain Henry, R.N. In the figure of the carapace of the Zrionye (Tri. subplanus) in Cuvier’s pl. xiii, fig. 5, ‘Ossemens Fossiles,’ tom. v, pt. ii, the costal plates do not bear the same numbers as the corresponding neural plates ; the anterior costal plate is marked a1, whilst the corresponding neural plate is 42; the rib or pleurapophysis of the first dorsal vertebra, which is marked ¢1, is short, and is applied to the under and fore part of the second rib which supports the first costal plate. In T. XVI, the dermal ossifications of the carapace bear the same letters and numbers as the homologous parts in the previous plates, and in the woodcut, fig. 1, p. 3. * Ibid., pl. 2, A. 50 FOSSIL REPTILIA OF THE LONDON CLAY. TRIONYX BARBARA. Owen. Tab. XVIZ. This species, like the Zrionya Henrict, is most satisfactorily and beautifully repre- sented by an entire carapace in the collection of the Marchioness of Hastings, to whose indefatigable researches in the locality of the Eocene sand at Hordwell Cliff, its discovery is due, and by whose skill, tact, and patience it has been faithfully restored from its original fragmentary state. The carapace is more slender in proportion to its length, and deeper or more convex in proportion to its breadth, than in the Zr. Henricit. In this species, as is shown in T. XVI, the breadth is greatest towards the fore part of the trunk; in the Tri. Barbare this is the narrower part, and increases in breadth towards the middle of the carapace ( p/4). The antero-posterior diameter or length of the nuchal plate is greater in proportion to its transverse diameter or breadth, and the arched ridge on its inner surface is less strongly developed than in Zi. Henrici. On the outer surface the smooth anterior border, where the plate would seem as if cut away obliquely to an edge, is more extensive in comparison with the rough, worm-eaten surface in the Zz. Henrici (T. XVI, fig. 3), or those in the nuchal plate of Z)r?. incrassatus, T. XVIII, fig. 1, ch. The median part of the anterior border is more deeply excavated, and the lateral borders less deeply dentated in the 777. Barbare. The whole of the posterior border of the nuchal plate is thick, sutural, and is articulated to the first neural plate and the anterior costal plates (p/1); the middle part extending backwards to unite with the neural plate, by which also 77. Barbare differs from Zri. Henrici. The first neural plate is shorter and broader in proportion to the length of the costal plates than in the Zi. Henrici, but presents a similar shape, the sides being parallel, and the posterior angles truncate; in the three succeeding neural plates the sides converge towards the anterior end, but the posterior angles continue to be cut off. The fifth neural plate is oblong and quadrangular, as in 777. Henrici, T. XVI. In the sixth neural plate the fore part is the broadest, and its angles are truncate; the seventh is a subtriangular and not fully-developed plate; the corresponding pair of costal plates meeting behind it. The eighth pair of costal plates (p/s) similarly supersede and take the place of ss, by meeting and joining at the middle line, but the left is the broadest, not the right. The first costal plate (pli) is longer in proportion to its breadth (or antero- posterior diameter), which is also more equally preserved throughout its length than in the 71. Henrici, and the connate smooth rib is less prominent on its under surface. The inner and anterior angles of this surface do not show the depression formed by the head of the vertical scapula, which is present in that part of the stronger Tri. Henrici. CHELONIA. 51 A well-marked distinctive character is also afforded by the seventh costal plate (plz), from which the free end of the connate rib projects at the anterior angle of the dilated end in Zvi. Barbare, and the free border of that end describes a straight line transverse to the axis of the carapace. The free borders of the eighth pair of costal plates are on the same transverse line, and the posterior part of the carapace is censequently truncate and straight. The lateral margin of the carapace is more gradually bevelled down, and to a less obtuse edge than in the 777. Henrici. The length of the carapace of the Zvi. Barbare, from the fore part of the first neural plate to the hind border, is nine inches and a half; the greatest breadth of the carapace, in a straight line across the fourth pair of costal plates, is nine inches ten lines. The total length of the carapace is eleven inches and a half. The free end of the connate rib projects entire from the fifth, sixth, and seventh costal plates. The character of the sculpturing of the outer surface of the costal plates is very similar to that in the Zi. Henrici: the tendency to the concentric arrangement of the raised lines is equally well marked in 777. Larbare, and is accurately given in Mr. Erxleben’s beautiful plate. The carapace is not only more arched transversely, but it differs from that of Tri. Henrici in being slightly depressed along the middle line, as is indicated in fig. 2, Te SV, . This beautiful species of 7rionyx is dedicated, with much respect, to its accomplished discoverer, Barbara, Marchioness of Hastings, and Baroness Grey de Ruthyn. TRIONYX INCRASSATUS. Owen. Tab. XVII, XVIII, and XIX. This species of Zrionyx, from EHocene formations of the Isle of Wight, resembles in general form the Zz. Henrici of the Hordwell sand, but differs from it in the anterior internal angle of the first costal plate (p/i, T. XVII and XVIII) being cut off, like that of the second and succeeding costal plates: it also differs in the greater length of the second costal plate as compared with the breadth of its outer end, and in the greater breadth of the outer end of the sixth costal plate (p/6, T. XVID), the outer or terminal border of which is more convex. The nuchal plate (ch, T. XVIII) articulates with the whole anterior border of the first neural (s1) and costal plates (p/i), but sends backwards a process from near the middle of its posterior border, which fits into the space left between the truncated antero-internal angles of the first costal plates and the first neural plate. In this respect it resembles the nuchal plate of 777. Barbare (T. X VIA), but the difference of general shape between this more delicately formed species, and the one under consideration, is well marked, and decisive as to their specific distinction. The 52 FOSSIL REPTILIA OF THE LONDON CLAY. anterior border of the nuchal plate of 777. ixcrassatus is smooth, slightly channeled, and feebly emarginate at the middle part; the plate sends out three short, tooth-like processes on each side; the posterior angle forms a fourth process which articulates with the true costal part, or end of the second rib, connate with the first costal plate (py/i). The first neural plate (s1, T. XVIII) is rather broader in proportion to its length than in the Zri. Henrici. The second (s2) and third (s3, T. XVII) do not expand so much behind; the vermicular pattern is broken into distinct tubercles upon these plates. The posterior lateral sides of the hexagonal neural plates are relatively longer than in those of 77. Henricit. The fifth neural plate (s5, T. XVII) extends backwards beyond the fifth pair of costal plates (p/5, compare with T. XVI) and articulates with the sixth pair of costal plates ; but the eighth and part of the seventh neural plates are superseded by ossification, extending from the seventh and eighth pairs of costal plates to the median line, where those plates articulate with each other, as in the Tri. Henrici and Tri. Barbare. The inner surface of the nuchal plate (cA, fig. 2, T. XVIII) is divided by a transverse, slightly interrupted ridge, gently concave backwards, into two nearly equal parts; the posterior one being most excavated. The inner surface of the first costal plate (p/i1, T. XVII and XVIII) presents the prominence (c2) left by the fracture of the vertebral end of the second rib, where it becomes connate with that plate, and also the oblique ridge (c1) formed by the attachment of the expanded end of the first short rib. The free end of the second rib (c2) is short, obtuse, depressed, convex above and flat below; the body of this rib has subsided to the level of the inner smooth surface of the costal plate, with which it has become completely blended. A small portion of the body of the second vertebra is preserved in connexion with the long neural arch, showing that it was slightly carmate at the under surface. The breadth of the third rib (c3), where it becomes connate with the second costal plate (p/2), is rather more than one third the breadth of that part of the plate ; the rib at first sinks almost to the level of the under surface of the plate, and then gradually rises, increasing in breadth to its free extremity. The true pleurapophysial portions of the succeeding costal plates (4, 5, 6, 7, 8, and 9, T. XVII) are better defined by outline grooves, but their degree of prominence is slight, except in the last pair (9), which have been liberated from the superincumbent costal plates (p/s) before they reached their posterior borders. The minute accuracy and beauty of Mr. Erxleben’s lithographs supersede the necessity of further verbal description of these rare and singularly well-preserved fossils. T. XVII gives an inside view of the almost entire carapace of the Zz. cncrassatus ; and T. XVIII gives an outside (fig. 1) and an inside view (fig. 2) of the fore part of the carapace of the largest individual of the same species of Zrionya, from the Isle of Wight, showing the nuchal plate (c/) in its natural articulation with the anterior neural and costal plates. CHELONIA. 53 One character by which these carapaces differ from those of the Zrz. Henrict or Tri. Barbare is the abrupt, almost vertical, border of the carapace, which is formed by the peripheral ends of the costal plates: these increasing in thickness as they approach that end, render the border characteristically thick: the specific name— incrassatus—has reference to this structure. The border is not grooved, and it is slightly produced above the projecting end of the subjacent rib, where it slopes a little down tothe connate rib (T. XVIII, fig. 1). This structure will serve to distinguish a detached costal plate of the Zi. zucrassatus from one of the Zit. circumsulcatus (T. XIXB, figs. 1, 2, 3); and the verticality and thickness of the margin will equally distinguish it from one of the 777. Henrici or Tri. Barbare. The chief value of the specimen (figured in T. XIX) is derived from the fact, that several other bones of the same skeleton were discovered with it; and these I next proceed to describe. T. XIX, fig. 1, is the entosternal piece of the plastron, having the characteristic form of the chevron ; it is broadest and most compressed at the median junction of the two crura, which increase in thickness and diminish in breadth as they diverge. The branches are relatively more slender than in the 77. Ayyptiacus* and Tri. Javanicus ;¢ they resemble those of the Zi. carinatust and Tri. gangeticus.\. Fig. 2 2’ is the lower branch of the left episternal : it is slender, gradually tapering to a point, flattened above or on the inner surface, convex behind, grooved along the margin next the entosternal. This piece, in its length and slenderness, resembles the corresponding part in the 777. carinatus and Tri. gangeticus. Fig. 3 3’ is the left hyposternal and part of the left hyosternal; the latter (4s) includes the mesial border, showing the relative extent of the angular part that sends off the ridged tooth-like processes, which are two in number, the anterior one notched or subdivided. The exterior, connate, rough, and tuberculate dermal plate stops at the base of these processes. The hyposternal (ps) has the nearest resemblance to that of the 77. gangeticus figured by Cuvier,|| but differs by the number of short toothed processes from its median and inferior border, and by the more slender base supporting the two long, lateral, striated, pointed processes. The tuberculate dermal plate covers all the exterior of the hyposternal to the roots of the pointed processes. The notch for the reception of the xiphisternal is rounded at the bottom. Fig. 4 shows the long, rib-shaped, but straight scapula (51); its head forms two thirds of the glenoid cavity for the humerus; the body, flattened behind, convex in front, gradually contracts as it ascends, and terminates in an obtuse point; the * Geoffroy, loc. cit., pl. 2, fig. B, o. + Ibid., pl. 3, fig. B, o. t Ibid., pl. 4, fig. B, o. § Cuvier, Ossemens Fossiles, tom. v, pt. ii, pl. 12, fig. 46. || Loe. cit. 54, FOSSIL REPTILIA OF THE LONDON CLAY. clavicular process (58) is shorter than the scapula, and slightly expands at its extremity. Both parts are longer and more slender than the homologous ones of the recent Zrionyex figured by Cuvier.* Fig. 5. The coracoid has the expanded, slightly curved form characteristic of the genus ; it is not so broad as that figured by Cuvier.t Fig. 6 is the iliac bone, short, thick, curved, subcompressed, attenuated and striated at its sacral extremity; the enlarged articular end is divided into three facets: two oblong and rough for sutural junction with the ischium and pubis; one smooth, and the smallest of the three, for the acetabulum. Fig. 7 is the almost entire right femur; its convex, long oval head, bends inwards from between the two trochanters, of which the external and largest is broken off. The shaft bends backwards, and gradually expands to the feebly divided convex condyles. All the characteristics of the modifications of the femur in the Zrionya are here preserved. Fig. 8 is a claw-bone, natural size. Fig. 9 9° 9” are three views of the sixth cervical vertebra of the same Zrionyz. This may be recognised by the broad, depressed, posterior surface of the centrum, partially divided into two cavities, side by side (c’) ; the seventh cervical has the two cavities there quite separated from each other; the fifth and preceding cervicals have the posterior surface of the centrum with a single cavity ; so that the sixth cervical is the only one which has a single convexity in front (c, fig. 9’), and a double concavity (c’, fig. 9”) behind. The body is long, slender, compressed in the middle, with one median inferior ridge anteriorly, and a pair of inferior ridges posteriorly ending in hypophysial tube- rosities (fig. 9, yy), which support, as it were, the posterior articular cups. A short, obtuse diapophysis projects from each side of the fore part of the centrum. The prezy- gapophyses (z) support slightly convex, oblong, articular surfaces ; the zygapophyses (2) are long, diverge, and support concave, oblong surfaces looking downwards. There is no spine; the neural arch is complete above the middle third of the centrum, the canal expanding towards both its wide, oblique outlets ; this modification of course relates to the great extent of motion between contiguous vertebre, and the necessity for providing against compression of the myelon during their rapid inflections and extensions. The specimens of 72. incrassatus here described are preserved in the Museum of the Marchioness of Hastings, by whose kind and liberal permission they, with other rare Chelonites, have been described and figured for the present Monograph. * Loc. cit., pl. 12, fig. 4. + Loc. cit., pl. 12, fig. 4. CHELONIA. rt Ot TRIONYX MARGINATUS. Owen. Tab. XIX+. A more obvious character than that pointed out at the peripheral border of the costal plate in Zrionyx incrassatus, and serving better and more readily to determine such elements of the carapace, is the ridge with minute parallel striae, which extends along the upper surface, close to the anterior and posterior borders of the costal plates in the species of Zrzonye which I have on that account distinguished by the specific name of marginatus. Mr. Erxleben has well given this character in the reduced view of the carapace (T. XIX +). The border-pattern gradually becomes narrower and fades away before it reaches the outer end of the costal plates; it is also wanting on the anterior border of the first costal plate (p/1), and on the posterior border of the last (p/s). The outer ends of the costal plates, which constitute the greater portion of the periphery of the carapace, are at first slightly bevelled off, and then vertically truncate ; the sloping or bevelled part having the fine fibrous surface, which I have compared to coarse linen cloth. The vertical part of the border is slightly excavated in the fifth and sixth costal plates, but not so deeply as in the 77. circumsulcatus, nor is the margin so thick in proportion to the length of the plate. The neural plates are relatively smaller, in comparison to the costal plates, than in any of the foregoing species, but they agree in number; the eighth being suppressed, and the seventh reduced, in the same proportion as in 77. Henrici and Tri. Barbare, by the median union of part of the seventh pair and of the eighth pair of costal plates. The fifth neural plate presents a simple oblong quadrilateral figure; the four neural plates in advance are six-sided, the two additional and shortest sides being formed by the truncation of the posterior angles; the sixth and seventh plates, on the contrary, have their anterior angles cut off. This modification in the form of the neural plates, and in their mode of juncture with the costal plates, relates to the opposite curvatures or inclinations of the costal plates, in the direction of the axis of the carapace: the anterior ones bending forwards, the posterior ones backwards, in addition to the curve common to all but the last pair of plates, transversely to the axis of the carapace, with the concavity downwards or towards the thoracic-abdominal chamber. The anterior internal angle of the second, third, and fourth costal plates is cut off; the posterior internal angle of the sixth, and both internal angles of the fifth pair of plates (pls). In these modifications of the form of the neural and costal plates, the 77. marginatus agrees with the Zi. Henrict and Tri. Barbare, and differs from the 777. encrassatus, in which all the neural plates but the seventh are six-sided, with the posterior internal angles truncated, Each of the costal plates, therefore, of the fifth 56 FOSSIL REPTILIA OF THE LONDON CLAY. pair, in the Z)i. cncrassatus, differs from those of the three other species of Zrzonyx here described, in having only the antero-internal angles truncated, instead of both these and the postero-internal ones. In the form and general proportions of the first pair of costal plates, the 777. mar- ginatus shows an intermediate character between the Zi. Henrict and Tri. Barbare ; in the great breadth of the peripheral end of the seventh pair of costal plates it differs in a well-marked degree from both species, and especially from the 777. Henrict, which it most resembles im its general contour. In the 777. cmcrassatus the seventh costal plates maintain nearly an uniform breadth from end to end. The antero-posterior diameter of each of the triangular plates of the last costal pair exceeds the transverse diameter, whilst these proportions are reversed in 77. Henrici ; the difference in part depending on the different form of the posterior border of the carapace in the Zt. marginatus, which is truncated ; the free borders of the last costal plates forming a straight transverse line. The marginal pattern of the costal plates may be traced in a slighter degree round the neural plates. The reticular sculpturing is better defined, and of a coarser pattern in the Zi. mar ginatus than in any of the previously defined species. The middle line of the carapace is slightly depressed, as in the 77ri. ncrassatus. The general degree of convexity of the carapace, which is less than that in the 77. Henrici and Tri. Barbare, agrees also with that of the Zr. incrassatus. The length of the carapace from the fore part of the first neural plate is eleven inches ; its greatest breadth, across the suture between the third and fourth neural plate, is twelve inches. This species is from the eocene deposit at Hordwell Cliff, Hampshire: it was discovered by the Marchioness of Hastings, and is preserved in her ladyship’s collection at Efford House. TRIONYX RIvosus. Owen. Tab. XVIILZ4. This beautiful species of Zrzonyz, also discovered by the Marchioness of Hastings in the Eocene beds at Hordwell Cliff, has fortunately a characteristic pattern of sculpturing, which, like that in the Zr?. marginatus, would serve for the determination of detached portions of the carapace. Any of the costal plates, for example, of the posterior half of the carapace, figured in Tab. XVIIL4, might be distinguished by the sub-parallel longitudinal, and more or less wavy ridges, superadded to the more common reticulate sculpturing from the homologous parts of the carapace of any of the preceding fossil species of Zrconya, and, so far as I have yet seen, from any of the recent species. The ridges in question, it will be understood, are longitudinal in respect of the CHELONIA. 57 entire carapace; they would be transverse to the long diameter of the detached costal plate; they become more wavy as they recede from the neural plates. Of these only the sixth (sé) has been preserved in the specimen described ; it differs in shape from that in any of the foregoing species, in being broader in proportion to its length ; its greatest breadth being, as in Zr. Henrici, Tri. Barbare, and Tri. marginatus, across its anterior fourth part. The fifth neural plate, as in the species above cited, has been an oblong quadrate one, the fourth plate has had its postero-internal angles cut off, contrariwise to the sixth. The fifth costal plates have accordingly the same character of truncation of both their internal angles, though less marked anteriorly. A portion of the seventh and the entire eighth neural plates have been superseded, as in the other fossil Zrionyces, by the median growth and junction of the seventh and eighth pairs of costal plates. In the forms and proportions of these plates the present species agrees best with the Zi. Henrict and Tri. incrassatus ; the latter species differs from it by the breadth and convexity of the sixth costal plates (plé). The smooth connate ribs (5, 6, 7), shown on the under surface of the costal plates, T. XVIILZ, fig. 2, preserve a more uniform diameter, and do not expand in the degree shown in the 7/1. incrassatus, T. XVII, 5, 6,7; the rib (gs) attached to the costal plate (y/7) is straighter in 777. rivosus than in 777. incrassatus. The projecting extremities of the ribs are beautifully preserved in the specimen of Tri. rivosus here described: their greater length, as compared with those attached to the fifth, sixth, and seventh costal plates in Zi. Barbare (TY. XVIA), depends upon the nonage of the present specimen, which is figured in T. XVIIL4 of the natural size. The peripheral borders of the costal plates are bevelled off obliquely from above downwards, and project a little where they join the end of the subjacent rib; the surface of this is finely and longitudinally striated. The reticulate sculpturing of the carapace extends to the sloping peripheral border, as it does to the vertical thick border of the carapace in 77. cucrassatus; it is not separated from the border by a marginal decussating fibrous surface, as in Zi. marginatus, Tri. Henrici, and Tri. Barbare. The longitudinal ridges of the carapace, which form the chief distinctive character of the 77. rivosus, offer an interesting though slight approach to the main feature of the carapace of the Luth or coriaceous soft turtle (Spargis coriacea); but in this existing species the longitudinal ridges or carinee are straighter and more elevated, and the surface of the carapace is smooth at the interspaces. The less parallel and wavy course of the ridges in the present extinct 7rionya give a sinuous course to the intercepted spaces, like the furrows left by streams of water which have temporarily coursed over a sandy surface, whence the name “ rivosus” proposed for the species. 8 58 FOSSIL REPTILIA OF THE LONDON CLAY. TRIONYX PLANUS. Owen. Tab. XIXC. This species, like the 7/7. rivosus, is represented by the posterior part only of the carapace, but the distinguishing characters are so well marked in it as to leave no doubt respecting the difference of the species from that of any of the above-defined Trionyces. 'The specimen consists of the last four pairs of costal plates, which are flat, with a coarse reticulate pattern on their upper surface, worn away towards the median end of the plates into a fossulate pattern, or detached pits; the reticulate sculpturing extends to the peripheral border of the costal plates, which is almost vertically cut down, and.is scarcely at all produced where the attached rib projects: there is no marginal pattern along the anterior or posterior borders of the costal plate. The ribs are more neatly defined from the superincumbent costal plates than in any of the foregoing species, except, perhaps, the Zz. rivosus. The Zi. planus differs from them all in the complete obliteration of both the seventh and eighth neural plates, and by a partial obliteration of the sixth neural plate. This arises from a similar encroachment of ossification from the postero-internal borders of the sixth costal plates, upon the dermal cartilaginous matrix of the sixth neural plate, to that which happens in respect of the seventh neural and costal plates in the other Zrzonyces ; whilst the whole of the seventh neural plate is superseded, as well as the eighth, and by the same encroach- ment of the corresponding pairs of costal plates. These modifications and varieties of the osseous parts of the carapace are very significative of the essentially dermal nature of those parts, and show the small value and deceptive tendency of that developmental character on which Cuvier and Rathké have relied in pronouncing the neural plates to be developed spimous processes of vertebre, and the costal plates to be expanded ribs. The connation of the seventh and eighth neural plates with the corresponding costal plates does not destroy their essential nature and existence, though it seems to make them part of the costal plates, any more than that connation with the neural arch in other Che/onia which seems to make them spinous processes. Another distinctive character in the Zi. planus, as compared with the foregoing Eocene species, is the very close union, almost amounting to confluence, between the seventh and eighth costal plates of the same side, the original suture between which has been almost obliterated at their inferior surface. In this character the 77. planus resembles the Tri. ferox, Schweigger (Gymnopus spimiferus, Dum. and Bibr.), and 771. muticus, Lesueur, but it differs from both by the flatness of its carapace, and the absence of any keel-like elevations upon its outer surface. The middle of the posterior border of the carapace is slightly concave. The specimen here described and figured was obtained by the Marchioness of CHELONIA. 59 Hastings from the Eocene sand of Hordwell Cliff, and forms part of her ladyship’s rich and instructive collection. With the above portions of carapace, and apparently belonging to the same species of Trionyr, were found the two osseous plates, naturally and suturally united together, which are figured in T. XIX J, fig. 6, 4s, ps ; they present a similar coarse reticulate pattern on their external surface, with the same tendency to a concentric arrangement of the raised parts towards the periphery of the plate ; their inner surface is smooth, slightly undulating, but upon the whole a little concave, and without any indication of adherent ribs. I regard them therefore as parts of the plastron, and they agree best with the hyosternal and hyposternal elements of the right side; yet differ in having no tooth-like processes extending from the inner border, which is convex instead of being concave, where the two elements join each other. At the inner and anterior angle of the hyosternal there is, however, the fractured base of what was probably a tooth-like process ; and there is similar evidence of such processes having extended from the posterior angle of the hyposternal, close to what I take to have been part of the notch for the xiphisternal. These fragments at least show that the 7Zri. planus, or whatever species from Hordwell they belonged to, must have had a very different form of plastron from that of the 7ri. incrassatus of the Isle of Wight, of which the conjoined hyosternal and hyposternal bones are figured in T. XVIL4, figs. 3 and 3%, and from that plastron of which the hyposternal piece, from Bracklesham, is figured in T. XIX J, fig. 7. TRIONYX CIRCUMSULCATUS. Owen. Tab. XIXB, figs. 1, 2, and 3. It may seem to have been hazarding too much to found a species on a single character when manifested by a single fragment of a carapace, which is all that at present represents such species ; yet the character in question is so strongly marked, and so different from that of the same part of the carapace of any other fossil or recent species of Zrionyzx, that there appears to be no other alternative than to regard it as specific. The character in question is the groove or canal which is excavated in the thick vertical margin of the expanded free extremity of the fourth costal plate of the left side, figured in T. XIX B, figs. 1, 2, and 3. The vermicular sculpturing of the external surface of this plate, and its proportions and connexions with the connate rib, prove it to belong to the carapace of a Trionyz. Previously to receiving this specimen from Lady Hastings, my attention had been drawn to the different modes in which the extremities of the costal plates of the different species of Zronyx were modified, in order to form the border of the carapace ; sometimes obliquely bevelled down to an edge, as in the 7. Barbare and the fragment of the Zrionya pustulatus, from Sheppy, figured in T. XIX.B, 7—10; some- 60 ; FOSSIL REPTILIA OF THE LONDON CLAY. times cut down vertically, or nearly so, as in the thickened border of Zvi. incrassatus ; sometimes with a marginal modification of the external sculpturing before the edge was formed, as in 77. marginatus ; sometimes without any such border-pattern, as in Tri. rivosus. But whatever character the border of a carapace has presented, has been constant in the same species, m which it is modified only at the fore part of the border formed by the nuchal plate, and at the back part formed by the short and small eighth pair of costal plates. From this, therefore, it is to be inferred that the peculiar modification presented by the free border of the fourth costal plate, T. XIX, fig. 3, was repeated in all the other costal plates, excepting, perhaps, the last pair; and consequently that the carapace was almost entirely surrounded by a thick, vertical border, deeply grooved,—a character which is expressed by the specific name circumsulcatus, selected to denote the Eocene Trionya, represented by the fragment of the carapace here described. This fragment, which consists as before said of the fourth costal plate of the left side, presents the common reticulate pattern of its external sculptured surface, but with some modifications not presented by the before-described species ; the meshes are smaller near the ends of the plate than at its middle part, and the network is finest near the peripheral end. In the 77. marginatus more particularly, and in a minor degree in Zri. tncrassatus, the Tri. Henrici, and Tri. Barbara, we observe the raised parts of the network assuming a linear arrangement, more or less concentric, with the circumference of the carapace; but there is nothing of the kind observable in the Tri. circumsulcatus. Yn this species also the outer surface of the costal plate presents a distinct though slight double curvature; the usual convexity being changed into a concavity near the peripheral border : and, as the inner surface presents the usual uniform concavity, the peripheral part of the plate suddenly augments in thickness as it approaches the grooved border. (See fig. 2.) The character which distinguishes the ‘Tri. incrassatus from Tri. Henrici, Tri. Barbare, and Tri. rivosus, is exaggerated in Tri. circumsulcatus, and there is added to it the groove, of which there is no trace in Tri. incrassatus, and but a feeble one in the fifth and sixth plates of 777. marginatus. The connate rib is almost wholly sunk into the substance of the superincumbent costal plate in the 7/7. circumsulcatus ; it is less prominent than in any of the foregoing species, especially at its distal part, which is also less expanded than in the 77. incrassatus. The free extremity of the rib is entire, and is very short, as is shown in ficure ]. TRIONYX PUSTULATUS. Tab. Kae, figs. 7, 8, 9. The contrast which the fragment above referred to, of apparently the homologous costal plate to the one last described, presents in the character of its peripheral CHELONTIA. 61 border, and in the prominence of the connate extremity of the rib on its under surface, is so great, as must impress the value of such characters upon the paleontologist. The outer surface of the present fragment presents a well-marked reticulate, or rather pustular, pattern, but a coarser one than in the 77. circumsulcatus. The reticulation is continued to the beginning of the bevelled border in fig. 7, which slopes gradually to an edge; beneath which the free end of the rib projects. The Zi. rivosus most resembles the present fragment in this character. The fragment is from Sheppy. I strongly suspect it to belong to a species distinct from any of those from Hordwell; and, in the hope of acquiring more illustrative specimens, the attention of collectors is directed to it by the specific name and the fizure here given. Trionyx. Sp. ind. Bracklesham. The left hyposternal bone of the Zrzonyz from Bracklesham (figured in Tab. XIX D, fig. 7) resembles that from the Hordwell Eocene, referred to Zrionyx planus (fig. 6, ps), in the convexity of the inner border at that part where it is concave in the 777. i- erassatus (T. XIX, fig. 3, ys); but it differs from the Zr7. planus in being uniformly convex as far as the xiphisternal notch, and is not indented before forming that notch, as it is in the 777. planus (T. XIXD). The present hyposternal shows also very plainly the base of a fractured tooth-like process of the subjacent heemapophysis projecting from the inner border, where there is no such trace of a process in the 777. planus. There are also the bases of a tooth-like process on both sides of the xiphisternal notch, and at the posterior outer angle of the hyposternal bone. The external border of the bone in advance of these processes is longer and straighter than in the corresponding part of the hyposternal of the 7/7. ‘acrassatus. The species of Zrionyx from Bracklesham cannot, however, be safely defined until the characters of its carapace are known. ‘The present specimen forms part of the valuable and instructive collection of Frederick Dixon, Esq., F.G.S. Family—PaLuDINOSa. This family, if regard were had to the number of species it contains, might be deemed the typical one of the order Che/onia. But in the series of extinct species, from the particular formation of Great Britain, to which the present Monograph is restricted, the number of marsh tortoises is small in comparison with those that were more truly aquatic (//uvialia), and which inhabited the sea (J/arina) ; and such a result might have been anticipated from the nature of their matrix, as it is elucidated by other classes of fossil animals, the remains of which are found in the London clay. The feet of the Paludinosa have the digits comparatively free ; more than three 62 FOSSIL REPTILIA OF THE LONDON CLAY. toes, as in 7e/ronyx, Lesson, and usually all five, are armed with claws, and are united together by a web only at their base ; but the extent of this web and the length and flexibility of the digits vary in the different species and sub-genera, and accordingly they manifest various degrees of aptitude for swimming, or for climbing the banks of the streams or marshes which they habitually frequent, and for walking on dry land. The costal plates extend, in the mature individuals, to the ends of the ribs, and articulate with the marginal plates; the dermal pieces of the plastron are co- extensive with the abdominal integument, and unite together by suture so as to form an unbroken expanse of bone; the sides of which, formed by part of the hyosternals and hyposternals, unite with a corresponding proportion of the lateral borders of the carapace. ‘There is a gradation in the degree of convexity of the carapace, and in the angle at which the sides of the plastron bend up to join the carapace, which pro- gressively brings the marsh tortoises nearer to the true land tortoises (Zerrestria), and some of the steps in this progression of affinities are illustrated by the fossils from the London clay. Those that, by the flatness of their carapace and plastron, depart least from the fluviatile forms of the order will be first described. Genus—PLATEMYS. PLateMys BuLutockil. Owen. Tab. XXI. Report on British Fossil Reptiles, Trans. British Association, 1841, p. 164. Amongst the fossil Chelonians of the London clay, the portable dwelling-house of which was provided with side walls as well as a floor and roof, are some tolerably large species, remarkable for the lowness of the roof of their abode, and especially for the flatness of its floor. A rigid comparison of the numerous species of the marsh-dwelling Chelonians, which the active researches of naturalists have brought within the domain of science, has led to their classification mto several groups, to which generic or sub-generic names are attached, and the fine preservation of the characteristic part of the skeleton of the specimen from Sheppy, figured in Tab. XXI, gives the opportunity for determining to which of these subdivisions of the genus Hmys of Bronguiart that specimen belongs. In my ‘Report on British Fossil Reptiles,’ the result of these comparisons, as regards the present fossil, were simply indicated by the sub-generic name, and I confined myself to a description of the specific distinctions noticeable in the only example I had then seen. The present species differs from all those to which MM. Dumeril and Bibron CHELONIA. 63 restrict the term Hmys,* by the presence of a thirteenth scute—the intergular one (7g. T. XXI) upon the plastron; from the genera Cistudo and Kinosternon it differs by the absence of any moveable joint between the parts of the plastron; from the Zetronywz by the rounded anterior border of the plastron, and the greater number of scutes that have left their impressions upon it: it resembles the genus P/latysternon in the flatness of the plastron and the horizontality of its lateral prolongations ; but it differs from the only known species of that genus in the contour of the sternum, which is elliptical and rounded in front, and has the lateral prolongations one third the length of the entire sternum. It has also the intergular scute, which is absent in the P/atysternon, as in the Lmydes of Dumeril and Bibron. The presence of this scute, so plainly indicated at 7g in the petrified plastron from Sheppy, together with the impressions of six pairs of the more constant scutes of the plastron, indicate that the depressed form of the probably estuary terrapene to which that plastron belonged, has appertained to the section which the eminent French Erpetologists above cited have called Plewroderes, or those that could retract their neck beneath the side only of the anterior aperture of their thoracic abdominal case. From the genus Peltocephalus the fossil under comparison differs by the marginal position of both gular (gv) and intergular (77) scutes, and by the slight narrow emargination of its posterior extremity (zs). An outline of the natural size of this emargination is added in the plate. It more nearly resembles the Podocnemys expansa in the forms and proportions of the plastron scutes ; but the three anterior ones (gu, gu, and 727), are not wedged in (enclavées) between the humeral scutes (4), but are on a plane anterior to them. The form and proportions of the plastron in certain species of the P/atemys, Dumeril and Bibron, and the number and relative position of the scutes which covered it, offer the nearest resemblance to those of the present fossil, and, with the results of the foregoing comparisons, have determined my reference of the specimen in question to that genus. Like the Platemys Spiavi (mys depressa of Spix), Platemys radiolata, Platemys gibba, and some others of the genus, the sternum is rounded at its anterior border, and notched at its posterior and narrower extremity. The intergular scute (?7) which crosses the median suture of the episternals (es) is sub-pentangular and larger than either of the gular pair; its point encroaches a little upon the entosternal bone (s). The gular scutes (gv) are triangular, and, with the intergular one, cover the anterior border of the plastron. The humeral or brachial scutes (4) are inequilateral quadrate plates ; the pectoral scutes (pe) and the abdominal scutes (a4) are transversely oblong and quadrate. The femoral scutes are inequilaterally quadrate, the posterior external angles being prolonged and rounded off. The anal scutes would be sub-rhomboidal were the posterior * Erpétologie Générale, 8vo, 1835, tom. ii, p. 232. 64 FOSSIL REPTILIA OF THE LONDON CLAY. end of the plastron entire. There are impressions of three scutes—the axillary, the inguinal, and a supplementary one,—upon each lateral prolongation of the plastron, covering the suture between this and the marginal plates of the carapace (aa), in which the present fossil resembles the Platysternon or large-headed Hmys of China; but the lateral walls are relatively longer, being equal in antero-posterior extent to one third the same diameter of the entire plastron ; whilst in the subgenus P/atysternon they are less than one fourth. The general form of the plastron is also very different; in the Platysternon megacephalum, e. g. the plastron has an oblong quadrilateral figure, with an open-angled notch behind. Retaining, then, the present species in the genus Platemys, as defined by Duméril and Bibron, we find that it enters into that small minority of the group in which the plastron is rounded instead of being truncate anteriorly. In the present remarkable fossil the plastron forms almost a long ellipse, the hinder, division beimg very little narrower, but tending to an apex, which is cut off by a shallow emargination. The lateral walls, of the length above defined, extend outwards almost parallel with the plane of the sternum, and expand to join by a wavy or rather zigzag suture the marginal plates; six of these (¢ @ a@ aaa) are preserved on each side; their lower sides form a very open angle with the lateral walls: but the fractures of these parts indicate that their horizontality may be in part due to acci- dental pressure. The anterior part of the entosternal (s) is bounded by two nearly straight lines, converging forwards at an angle of 65°, with the apex rounded off; the posterior contour of this bone is nearly semicircular. The length of the entosternal is two inches ten lines; its breadth three inches seven lines; the forms and relative positions of the other elements of the plastron are sufficiently illustrated by Tab. XXI: es, es marks the extent of the left episternal; 4s, 4s are the hyosternals ; ys the hyposternals; vs the xiphisternals. The chief peculiarity of this plastron is the intercalation of a supernumerary piece of bone, bearing the letters ye and ad between the hyosternal and hyposternal elements on each side; so that the middle third of the plastron is crossed by two transverse sutures instead of one; each suture being similarly interrupted in the middle by an angular deflection from the right, half an inch back, to the left side. The extremities of the transverse sutures terminate each at the apex formed by the inner or lower border of the parallel marginal plates. The first or anterior of these sutures is distant from the anterior margin of the plastron six inches five lines; the second suture is distant from the same margin eight inches nine lines; the right half of the suture, which is a few lines in advance of the left, is the part from which these measurements are taken. Since this deviation is rare, it having been noticed for the first time in the original description of the present specimen, a naturalist, not having the specimen at hand for CHELONIA. 65 comparison, might at first be led to suspect that the transverse impressions of the second (pectoral) or third (abdominal) pairs of scutes had here been mistaken for a suture ; but due care was observed to avoid this error; the scutes of the plastron have left obvious impressions at ye, fe, which prove that they were in the same number as in the Platemydians generally, and were quite distinct from the sutures in question. Thus the intergular scute (7g) is in the form of an ancient shield; the gular scutes (gz) are small inequilateral triangles, with their posterior border parallel with that of the succeeding pair of scutes. The posterior transverse boundary of these,—the humeral scutes (4~)—crosses the plastron four inches and a half from its anterior margin ; that of the pectoral pair of scutes crosses at seven inches and a half from the anterior border, and between the two transverse sutures; that of the abdominal pair (a6) at ten inches distant from the anterior margin, and about one inch and a quarter behind the second transverse suture; passing straight across the plastron between the posterior concave margins of the lateral wall. The posterior boundary of the fifth or femoral pair of scutes (fe) inclines obliquely backwards from the median line, as usual; it is three inches behind the preceding transverse impression. It is in the interspace of these impressions that traces of the transverse suture between the hyposternals and xiphisternals are obvious, about four inches from the posterior extremity of the plastron. If these traces were not so obvious, it might be supposed that the xiphisternals were of unusual length, entering into the formation of the lateral wall, and extending backwards from the second transverse suture to the end of the plastron; but this disproportion would be hardly less anomalous than the existence of the additional pair of bones intercalated between the hyo- and hypo- sternals which the present fossil evidently displays. In most of the existing large Hmydes and Platemydes, the median transverse suture traverses the plastron a little behind the third pair of scutes, and so crosses the fourth or abdominal pair (a4, ad); and according to this analogy, the second transverse suture in the fossil agrees with the single one ordinarily present, and has most right to be regarded as the normal boundary between the hyo- and hypo- sternals. One of the most distinctive characters of the present extinct Platemys is, therefore, the division of each hyosternal into two, the plastron consisting of eleven instead of nine pieces; if the very interesting anomaly which it displays be not an accidental or individual variety. Viewed in the latter light, its explanation is sug- gested by that homology of the hyosternals and hyposternals which determines them to be connate and expanded abdominal ribs (hamapophyses), and thus we may view the oldest of the known Platemydians as exhibiting, like many other extinct forms, a nearer approach to the more typical condition of the abdominal ribs, as they are shown, e. g. in the Plesiosawrus. Whereas, on Geoffroy’s hypothesis, that the plastron is the homologue of the sternum of the bird, it would be a further deviation from that type. 9 66 FOSSIL REPTILIA OF THE LONDON CLAY. The fine example of Platemys Bullockii, here described and figured, was purchased for the British Museum at the sale of Mr. Bullock’s collection. I am happy in the opportunity of expressmg my acknowledgments to hares Konig, K.H., F.R.S., for the urbanity with which every requisite facility was afforded. PLATEMYS BoWERBANKII. Owen. Tab. XXIII. Report on British Fossil Reptiles, Trans. British Association, 1841, p. 163. This species is represented by a fine specimen exhibiting not only the plastron (fig. 2), but likewise a great portion of the carapace (fig. 1), from Sheppy, in the rich collection of the fossil remains from that island in the possession of J.S. Bowerbank, Esq., F.R.S. It equals in size the Platemys Bullockii, in the British Museum, but differs in the absence of the finely punctate character of the exterior surface of the bones; in the greater antero-posterior extent of the lateral walls, and the longer curves which they form in extending from the body of the plastron. The carapace (fig. 1) presents the same equality of breadth of the neural plates (s2—s7) as in the mys testudiniformis ; but they diminish more rapidly in length as they recede in position; and the whole carapace is much more depressed ; it is flat along its middle tract. The sixth neural plate (s6) is a hexagon of nearly equal sides ; the seventh (s7) is a pentagon; the mesial or vertebral ends of the seventh pair of costal plates (y/7) meet and unite behind it, so as to conceal or supersede the eighth neural plate. In the circumstance of the neural plates decreasing in length without losing breadth, as well as in the mutual junction of the seventh costal plates, the present fossil resembles the Sheppy carapace from Mr. Crow’s collection, which Cuvier has figured, and which may, therefore, have belonged to the present species of Platemys. The plastron (fig. 2) is thirteen inches in length and ten inches in breadth; it is rather broader before than behind, rounded at the anterior border, with a shallow emargination at the middle of the posterior border, but wider than in the Platemys Bullocku, and with the angles on each side rounded off. The under surface is nearly flat, slightly convex at the fore part, and as slightly concave behind. The lateral walls uniting the plastron to the carapace are five inches in antero-posterior extent. The entosternal (s) resembles that of the Platemys Bullockii in general form, but is longer than it is broad, instead of the reverse proportions. The two anterior sides meet at a right angle. The episternals (es) are broadest behind. The middle part of the plastron is almost equally divided between the hyosternals (4s) and hyposternals (ps). There is a trace of the intercalary piece (4p), which is seen extending across the plastron of the Platemys Bullocki ; here it is wedged into the outer interspace of those bones, like one of the external portions of the composite abdominal ribs in the Plesiosaur. In the relative length of the lateral walls the Platemys depressa most resembles the present species. CHELONTA. 67 Genus—EMYS. EMYS TESTUDINIFORMIS. Owen. Tab. XXIV. Report on British Fossil Reptiles, Trans. British Association, 1841, p. 161, Emys pe Sueppy. Cuwv. (?) From the preceding genus of the Chelonia paludinosa the present species differs in the depth of the bony cuirass, the convexity of the carapace, and the concavity of the plastron (T. XXIV, fig. 6). The more immediate affinities of the present fossil are elucidated by the comparison of the points of structure which it displays with the anatomical characters of the carapace of the Platemys and Testudo. The specimen, on which the species here called Lmys testudiniformis is founded, includes a large proportion of the first, second, third, fourth, fifth, and sixth, with a fragment of the seventh costal plates of the left side; asmall proportion of the second, third, fourth, fifth, and sixth neural plates; the hyosternals and hyposternals, and part of the entosternal bones of the plastron. The first costal plate is one inch ten Imes in greatest breadth, one inch five lines broad at its junction with the neural plates, and four fifths of the vertebral margin is articulated with the second neural plate; one fifth part, divided by an angle from the preceding, joims a corresponding side of the lateral angle of the third neural plate; in this structure it resembles both the genus Zestudo and some species of Lys. The third, fourth, fifth, and sixth neural plates are of equal broadth, as in Lmydes ; not alternately broad and narrow as in the Zestudines ; they are likewise of uniform figure, as in most Hmydes; not variable, as in TZestudines; the neural plates also resemble those of the existing Hmydes, and particularly of the Box-terrapin (Cistudo) in form. The lateral margin of each is bounded by two lies, meeting at an open angle, the anterior line is only one fourth part the length of the posterior one; and this resemblance may be stated with confidence, since the portion of the entosternal piece preserved in the plastron determines the anterior part of the fossil. The costal plates preserved in the present Chelonite differ from the corresponding ones of the tortoises, and resemble those of the Lmydes in their regular breadth, and the uniform figure of the extremities articulated with the vertebral pieces; the anterior line of the angular extremity is nearly three times as long as the posterior one. Further evidence of the relation of the present Chelonite to the fresh-water family is given by the impressions of the epidermal scutes; those covering the vertebral plates (scuta vertebralia) agree with those of most Hmydians in the very slight production of the angle at the middle of their lateral margins, which is bounded by a line running parallel with the axis of the carapace, except where it bends out to form that small angle. 68 FOSSIL REPTILIA OF THE LONDON CLAY. The middle part of each side of the plastron, in the Hmys testudiniformis, is joined to the carapace by a strong and uninterrupted bony wall, continued from a large pro- portion of the hyosternal and hyposternal bones upwards to the marginal costal pieces. The median margin of the hyosternals and hyposternals are articulated together by a linear suture, traversing the median line of the plastron, and only broken by a slight angle formed by the right hyposternal, which is a little larger than the left. A similar inequality is not unusual in both tortoises (Zestudinide) and terrapenes (Himydide). The transverse suture is, of course, broken by the same inequality ; that portion which runs between the left hyosternals and hyposternals being two or three lines in advance of the one between the right hyosternals and hyposternals. The-posterior half of the broad entosternal piece is articulated to a semicircular emargination at the middle of the hyosternals; so that the whole plastron forms one continuous plate of bone. This is relatively thicker than in existing Hmydes, resembling in its strength that of tortoises ; and it is likewise slightly concave m the middle, which structure is more common in tortoises than in Emydians, save those in which the sternum is moveable ; in most of the other species the sternum is flat or slightly convex. I have shown in my paper on the Turtles of Sheppy,* that the carapace figured by Cuvier} was not sufficiently perfect to decide the affinities of the Chelonian to which it belonged ; if the vertebral scutes were less broad and angular than in marine turtles, the neural plates—much less variable in their proportions—were, on the other hand, as narrow as in turtles. But with reference to the plastron of the Sheppy Chelonite, figured by Parkinson,t and supposed by Cuvier to belong to an Hmys of the same species as the carapace above alluded to, I have been able to determine, by an exami- nation of the original specimen in the museum of Professor Bell, that ‘it belonged to the marine genus Chelone and to the species Jongiceps. In the fossil Amys in Mr. Bowerbank’s collection, the plastron being in great part preserved, establishes its nonconformity with the marine turtles, and manifests a striking difference from Parkinson’s fossil plastron. The entosternal piece is impressed, as in Tortoises and Emydes, by the median longitudinal furrow, dividing the two humeral scutes ; the transverse linear impression dividing the humeral from the pectoral scutes traverses the hyosternals half an inch behind the suture of the entosternal; the second transverse line, which divides the pectoral from the abdominal scutes, is not so near the first as in tortoises, but bears the same relation to the transverse suture of the plastron as in most Emydes; it does not pass straight across the plastron, but the right half inclines obliquely inward to a more posterior part of the median suture than is touched by the left half. The third transverse line, which divides the abdominal from the femoral scutes, passes straight * Geological Proceedings, December 1, 1841. + Ossemens Fossiles, tom. v, part iv, pl. 15, fig. 12. t Organic Remains, vol. iii, pl. 18, fig. 2. CHELONIA. 69 across the plastron between the posterior ends of the bony lateral walls, uniting the carapace and plastron. Inches. Lines. The breadth of the plastron is : - : : : 5 10 The outer posterior extent of the lateral wall is 3 9 The breadth of the entosternum . - n ‘ é 1 5 The depth of the whole bony cuirass at the middle line is 4 0 In the convexity of the carapace and relative depth of the osseous box, the Sheppy Chelonite slightly surpasses most existing species, resembling in this respect the Hinys ocellata and Cistudo Carolina. ‘The plastron is also slightly concave, as in the male of Cistudo vulgaris: it is, however, entire at the line where the transverse joint of the plastron exists in the box-tortoises ; and the extent and firm ossification of the lateral supporting walls of the carapace forbid likewise a reference of the fossil to those genera. The general characters of the present fossil, more especially the uniformity of size and breadth of the preserved vertebral plates and ribs, prove it to be essentially related to the fresh-water or Emydian Tortoises. It exceeded in size, however, almost all known Emydians, and was almost double the dimensions of the Emydian species (Cistudo Europea) now inhabiting central Europe. It appears, like the Cistudines, to have approached the form of the land tortoises, in the convexity of the carapace, but without possessing that division and hinge of the plastron which peculiarly distinguishes the box-tortoises. The contraction of the anterior aperture of the bony cuirass, especially transversely as compared with the Platemydians, would indicate more restricted powers of swimming, and consequently more terrestrial habits. In the thickness and strength of the bones of the buckler, especially of the sternum, we may discern an approach to the genus Zestudo. Assuming that the Chelonite here described may be identical with that of which the carapace from Mr. Crow’s collection is figured in the ‘ Ossemens Fossiles,’* the “ Emys de Sheppy’ of Cuvier will be one of the ‘‘synonyms” of the present species. Mr. Gray, in his ‘ Synopsis Reptilium,’ 8vo, 1831, has given Latin names to all the fossil reptiles indicated or established by Cuvier, and has called the “ Hmys de Sheppy” “ Emys Parkinsonii,” referring as representations of this species, not to the figure of the carapace above cited, which may belong to the same species as the present Himys, but to the figure of the plastron, copied by Cuvier from Parkinson’s ‘Organic Remains,’ and to the figure of the skull in the same work, both of which most unquestionably belong to the genus Chelone and not to the genus Lmys. The “ Hmys Parkinsoniz” of Mr. Gray is a synonym of my Chelone longiceps. Cuvier’s name,—which, besides the claim of priority, is the result of laborious and direct comparison devoted to the elucidation of its subject,—if rendered into Latin would be Hmys toliapicus ; but as the species to which it refers may not be the one * Ed. 1824, vol. v, part ii, pl. 15, fig. 12. 70 FOSSIL REPTILIA OF THE LONDON CLAY. here described, and is by no means the only fresh-water tortoise which the clay of Sheppy has yielded ; and since the characters of the present species have not hitherto been defined nor its affinities to the land tortoises been pointed out, the interests of science appeared to me to be best consulted by giving a distinct name to the present species. a The fossil here described is from the Eocene clay of Sheppy Island, and forms part of the collection of J. S. Bowerbank, Esq., F.R.S. Emys t&zvis. Bell. Tab. XXII. The only specimen I have seen of this species, I obtained from Sheppy a few months since, and it is now in my collection. It has some remarkable peculiarities which distinguish it, at first sight, from every other species of Emydian, either recent or fossil. The specimen is imperfect at each extremity ; the carapace wanting anteriorly the nuchal plate, and posteriorly from the eighth neural plate inclusive. The contour of the carapace is remarkably even, free from all inequalities of surface, and forming, from side to side, nearly a perfect segment of a circle, uninterrupted by either carina or depression of any kind. The whole surface of the bone also is remarkably smooth. The first neural plate (fig. 1, s1) is narrow, being not more than two fifths as broad as it is long; the sides parallel for the first two thirds of its length, then slightly narrowed; its sides are not interrupted by the costal sutures, as the posterior margin of the first costal plate (p/1) joms the anterior part of the second neural. The second, third, and fourth neural plates (s2—s4) are of an elongated hexagonal form, and nearly resemble each other ; the fifth, sixth, and seventh (s5—s7) are also hexagonal, but each shorter than the preceding one; the sixth is narrowed somewhat abruptly, and the seventh still more so, the latter being also shorter than it is broad. Although the posterior part of the carapace is considerably broken, there appears evidently to be an interval between the seventh and eighth neural plates; at which part the posterior portion of the seventh costal plate and the anterior portion of the eighth approximate to the corresponding plates of the opposite side, on the median line, without the intervention of the neural plates; a peculiarity which I do not remember to have seen in any other of the Lmydide. The first costal plate occupies in its breadth the whole length of the first neural, and the anterior fifth only of the second; but in consequence of the gradual shortening of the neural plates in the portion of each, posterior to the angle at which the costal sutures join them, the seventh neural receives the costal suture at about the middle of its length. CHELONIA. 71 The marginal plates (fig. 3, a, a, a) are broad, smooth, and curved evenly to the edge, where they turn under at nearly a right angle. The second and third vertebral scutes(v2, 3) are twice as broad as they are long, the outer angles being nearly right angles; and this must be, to a great extent, a permanent character, as the specimen is evidently not young. The fourth vertebral scute (v4) is hexagonal, and its breadth is about one fourth greater than its length. Of the plastron (fig. 2), the whole of the anterior portion is wanting, including the entosternal, the episternals, and a portion of the hyosternals; and the posterior portion has lost the greater part of the xiphisternals. The bones which remain form a broad, somewhat convex, uniform surface. The most remarkable circumstance connected with this part of the osseous box is the existence of a pair of intercalated, irregularly-formed bones (/~), which stand between the marginal portion of the hyosternal (4s) and hyposternal bones. These would appear to represent the pair of additional bones which will be seen in Platemys Bullockit (Tab. X XT), stretching across between the hyosternals and hyposternals, and, in the latter case, meeting like them in the median line. I have examined many skeletons of Emydes, but have never observed any similar structure in this genus; but in the genus Zerrapene, including the ordinary box- tortoises, there appears to be, in some cases, a rudiment of a corresponding bone.* The total length of the carapace of this specimen, judging from comparison with perfect recent examples of the same genus, was probably rather more than eight inches, and its breadth is six inches. Ts ee Emys Compronl. Sell. Tab. XX. The beautiful specimen of fresh-water Chelonia which forms the subject of the present description, is in the collection of the Marquis of Northampton, who has kindly allowed me the use of it, and to whose respected name I have dedicated it. The general form of this species, as well as many details of its structure, is so similar to that of a typical land tortoise, that it is difficult at first to reconcile its aspect with the idea of its being at all aquatic in its affinities. It is, however, doubtless a true Emys; and although the present specimen is a young one, its characters are sufficiently marked to enable us to distinguish it from every other. The costal plates * The sternal bones appear liable to occasional curious anomalous variations. Thus, whilein Platemys there is a perfect pair of intercalated bones between the hyosternals and the hyposternals, and in the present species an approach to a similar interpolation, we find, on the contrary, in Gymnopus, a genus of Trionychide, the only skeleton of which in this country I have now in my possession, the hyosternals and hyposternals constitute but a single bone on each side, a peculiarity which I believe to be perfectly unique in the whole of the Chelonian order. [T. B.] 72 FOSSIL REPTILIA OF THE LONDON CLAY. had not become ossified to the extremity of the ribs, and there is consequently a space between the costal and marginal plates, interrupted by the free extremities of the ribs, which just reach to the marginal plates. It is the only specimen of the family which I have seen, amongst the fossil Chelonian remains, in which the whole series of neural plates, with the nuchal and pygal, remain without material injury; and the plastron is also nearly entire. The nuchal plate (fig. 1, cZ) would form a triangle with its posterior angle obtuse, but that this angle is truncated for its articulation with the first neural (s1). This latter plate is quadrate, a little longer than broad, and rather narrowed forwards. The second (sz) and third (s3) are also quadrate, and nearly equilateral, The fourth (s4) is, however, rendered hexagonal by the termination of the costal suture at a short distance from the anterior margin; it is quite as broad as it is long. The fifth neural plate (s5) is of a similar form, but notably longer than it is broad, forming a broad hexagon, with the lateral angles nearer the anterior than the posterior margins. The seventh (s7) is the only one which forms a nearly symmetrical hexagon, broader than it is long, but with the lateral angles equidistant from the anterior to the posterior margins. The eighth and ninth neural plates (sg, 9) are regularly quadrate, the former being broader than it is long, the latter forming a perfect square. It is very remarkable how much more closely the seventh and following neural plates to the tenth are united than any of the anterior ones ; indeed the sutures between the seventh and eighth, and between the eighth and ninth, are with difficulty observable, notwithstanding the youth of the individual. The tenth neural (s10) and the pygal (p) plates are somewhat injured and bent down abruptly by some violence. I have dwelt somewhat in detail upon the direction of these plates, as their cha- racters evidently bear upon the near relation of this species to the terrestrial type already alluded to. The internal margin of the first costal plate (p/1) exactly coincides with the length of the first neural. The second and fourth costal plates (/2, 4) expand towards the margin of the carapace, and the third and fifth (/3,5) become narrower in the same direction in a similar degree. The marginal plates present no important peculiarity in this young specimen. With regard to the impressions left by the horny scutes, we find that although they are of the ordinary general form, they are less broad and spreading in proportion to their length, than is ordinarily the case in the Hmydide, and particularly in immature age; thus offering another character approaching the terrestrial type. The plastron (fig. 2) is tolerably perfect, and presents the remarkable expanse which ordinarily characterises the land and fresh-water forms, but especially the former ; and the anterior and posterior openings between the carapace and the plastron, for the exit and play of the extremities, are somewhat contracted, and thus appear scarcely to afford sufficient room for the natatorial habits of an aquatic species. CHELONIA. 73 The entosternal plate (s) forms an almost regular rhomb; the episternals (es) are much broken, and offer no peculiarity in the parts which remain; nor is there, in the general form of the hyosternals (4s) or hyposternals (ys), or the xiphisternals (zs), anything which calls for particular notice. The contour of the bony case, viewed as a whole, bears out the close relation to the terrestrial form which I have assigned to this species. The slightly curved costal regions of the carapace, and the even flatness of the vertebral portion, as well as the outline of the dorsum, when viewed laterally, show a very striking approximation to the small African species of true Testudo, 7’ areolata, and still more to 7. siguata. But if its geological position did not of itself preclude our considering it as belonging to a terrestrial group, the structure of many parts of its osteology would be sufficient to justify our considering it as a true Emydian. Inches. Length of the carapace . - : : : : : : : 3°2 Breadth of ditto. : : : : - : ; . : 2°9 Height of the bony case : : 7 4 : : : : 1°3 PB. EMYS BICARINATA. Bell. Tab. XXV and XXVI. The specimen before me, the only one which I have yet met with of this species, is very large, and, from the close union of the bones, and the nearly obliterated condition of the sutures, is evidently of considerable age; a fact also attested by the forms of the vertebral scutes (v2, v3, v4, T. XXV), which have become greatly narrowed in proportion to their length. The general outline of the carapace must have been nearly orbicular. The elevation moderate; the part occupied by the vertebral scutes, and about half an inch on each side of them, flattened; and this plain portion bounded on each side by a low obtuse carina, which is itself obscurely and irregularly grooved longitudinally. The sides are considerably sloping, with but a slight curvature. The carapace is wanting anteriorly in nearly the whole of the nuchal plate, and posteriorly from the tenth neural inclusive. At the sides a few fragments only of the marginal plates exist. The first neural plate (s1) is nearly oval, and, as usual in this family, is wholly included within the first pair of costal plates; it is considerably longer than any of the succeeding ones. The second neural (s2) is nearly as broad as it is long, the anterior angles truncated as usual, posteriorly somewhat narrowed ; the third neural (s3) has the peculiarity of being longer than even the second, and is less narrowed behind ; the fourth to the seventh inclusive (s4-7) are gradually shorter, the seventh forming a broad hexagon, with the lateral angles (meeting the costal suture) nearly midway between the anterior and posterior margins. The eighth (sg) is also broader than it is 10 74 FOSSIL REPTILIA OF THE LONDON CLAY. long, but the lateral angle is near the anterior margin, as in the preceding plates. The ninth (s9) is somewhat expanded posteriorly, but less so than usual. The sixth and seventh of the neural plates are considerably raised towards the centre, but with a slight longitudinal depression along the median line; and there is a considerable triangular or wedge-shaped elevation, commencing with its base near the anterior margin of the eighth, and extending to the posterior margin of the ninth neural plate. The costal plates (y/1—s) differ from those of the species in general in being more regularly parallel at their lateral margins. The first vertebral scute reaches to the posterior third of the first neural plate (v1), and its lateral margins are expanded forwards, but with a slight curve. The second and third (v2, 3) have nearly parallel sides, and are both longer than they are broad, the lateral angles being extremely inconsiderable ; the fourth (v4) is hexagonal, but still with short lateral angles; the fifth (v5) has the lateral margins, and, as usual, becomes broader posteriorly. As the costal or lateral scutes depend, in the only important and variable part of their contour, on the form of the margins of the vertebral, it is unnecessary to describe them. The plastron (T. XX VI) occupies about its usual relative proportion to the carapace, but it has been so much broken as to afford but little opportunity for any satisfactory or useful description. It would appear, however, from the extent of the openings for the passage of the limbs, that the animal must have possessed considerable powers of swimming, offering in this respect a very marked contrast to the testudiniform character of /. Comptoni and L. testudiniformis. Foot. Inches. Lines. Probable total length of the carapace. - : ] 0 0 Probable total breadth of ditto. : ; ; 6 0 10 0 Depth of the bony case ; : 5 5 3 . 0 3 3 Emys Devaspecui. Sell. Tab. XXVIII. An almost gigantic specimen of the fluviatile form of scutate Chelonia, in the collection of the Geological Survey, forms the subject of the present description. It is from the London clay of the Island of Sheppy. This species far surpasses in size any known Emydian, whether fossil or recent; the carapace having been certainly not less than one foot nine inches in length and one foot five inches in breadth. It very clearly belongs to the form to which I have assigned it, and in some of its broader characters approximates considerably to the last species, 7. bicarinata. The specimen is, however, unfortunately so badly injured, partly by having been originally much crushed, and partly by recent disintegration, CHELONIA. 75 from the decomposition of the pyrites with which it is extensively permeated, that the description must necessarily be confined to little more than general contour. The osseous case is somewhat less deep, in proportion to its probable length and breadth, than in Z. dicarinata, as will be seen by a comparison of their dimensions ; it is consequently less sloped at the sides, which are also less curved. There is not the slightest indication of a carina, either median or lateral; but the whole vertebral region is simply flattened. I have already had occasion to observe, that as the scutate Chelonians continue to grow, the vertebral scutes are observed to alter their form, and the relative proportion of their longitudinal and transverse diameters. This takes place particularly by the comparative abbreviation of the angular lateral projections which meet the line of junction of the margins of the corresponding costal scutes. These angles, as the animal grows, and as the scutes increase in size, become comparatively much shorter and more obtuse ; and to such an extent does this take place, that in many species the sides of the vertebral scutes become very nearly parallel in old age; as may be observed in the figure of 7. dicarinata (T. XXV), and in most recent species. Now the specimen at present under notice, notwithstanding its great size, exhibits this indication of old age, even in a less degree than in the figured specimen of E. ticarinata. We could not, therefore, even if other distinctive characters were absent, for a moment confound them as one species. In longitudinal dimensions the scutes in question ordinarily increase in proportion to the growth of the animal ; and afford, in the examination of mutilated fossil Chelonian _remains, approximating data for ascertaining the general size of the animal; the second and third vertebral scutes, taken together, being generally rather less than two fifths of the total length of the carapace. The edge of the present specimen, and the injuries it has undergone, combine to render any satisfactory account of the vertebral series of osseous plates impossible; the nuchal and pygal plates being absent, and the neural wholly indistinguishable ; and the plastron has been even more mutilated than the carapace. The impressions of the vertebral scutes are tolerably perfect, as far as regards the second (v2), third (v3), and fourth (v4). The second and third are about as broad as they are long, irregularly hexagonal, and the lateral angles are but moderately produced ; the third has the posterior margin shorter than the anterior; the fourth is rather longer than it is broad, and notably narrowed posteriorly. The plastron exhibits at least the usual expanse of form which belongs to the typical Limydes, but its condition is such as to preclude any detailed description. Feet. Inches. Lines. Probable length of the carapace. . . : . 1 9 0 Probable breadth of ditto . ; : ‘ : : i! 5 0 Depth - ; : ; : : ; : : 0 4 8 76 FOSSIL REPTILIA OF THE LONDON CLAY. Such are the meagre details to which we are restricted in describing by far the largest of all the fossil species of this genus. I have the gratification of offering it by name to my distinguished friend Sir Henry De la Beche, through whose kindness I have the opportunity of including it in the present Monograph. Be -B: FRAGMENTARY REMAINS OF EMYDIANS. Emys crassus. Tab. XXVII. From several such specimens kindly transmitted to me by the Marchioness of Hastings, I have selected for the subjects of Tab. XX VII two portions of a plastron; viz. the hyosternal (figs. 1, 1’) and the hyposternal (figs. 2, 2’). They are chiefly remarkable for their thickness (fig. 3), and also for their size in other dimensions. The hyosternal shows on its outer surface (fig. 1) very strong impressions of the interspace or union between the humeral and pectoral scutes, and between the pectoral and abdominal scutes. The hyposternal shows the same kind of impression between the abdominal and femoral scutes. These specimens were discovered in the Eocene sand at Hordwell, and are in the museum of the Marchioness of Hastings. In Tab. XXIV, figs. 1—5, are figured some portions of the carapace of an Limys, from the Eocene deposits on the north shore of the Isle of Wight. These also form part of the collection of the Marchioness of Hastings. PRINTED BY C. AND J. ADLARD, BARTHOULOMEW CLOSE, — Se eee 6hOV ee TAB. I. Skull of Chelone breviceps, nat. size. Fig. 1. Side view. 2. Top view. 3. Base view. 4. Back view. The following numerals indicate the same bones in each figure. STo BP WD = ,@ . Basioccipital. . Exoccipital. . Supraoccipital. . Paroccipital. . Basisphenoid. . Parietal. . Mastoid. i Ee 12. 14. 21. 26. 27. 28. 29, 29. 30. "Ons Frontal. Postfrontal. Prefrontal (with connate Nasal and Lachrymal). Maxillary. Malar. Squamosal. Tympanic. Articular. Surangular. Angular. Dentary. Devkel deh ef Lith Day k Son th” to the Cueen "wet TAB. 11: Chelone breviceps, four fifths of the natural size. Fig. . Upper view of the carapace. ch. The nuchal plate. s1—s10. The neural plates, most of which are connate with the neural spines. pli—pls. The costal plates, connate with the pleurapophyses or vertebral ribs. vi—v4. Impressions of the vertebral scutes. m. The first marginal plate. —_ iN) . Under view of the plastron and bent-down skull. es. Kpisternal element of plastron. hh. Hyosternals. ps. Hyposternals. vs. Xiphisternals. 3. Side view of skull. 7. Parietal. 8. Mastoid. 11. Frontal. 12. Postfrontal. 21. Maxillary. 26. Malar. 27. Squamosal. 28. Tympanic. 4. Outline of the transverse section of the middle of the thoracic-abdominal case. LE Day & Son lith “w the Queen DinkeL, det eb litt TAB. III. Skull of Chelone longiceps, nat. size. Fig. 1. Side view. 2. Top view. 3. Base view. 4. Back view. The same numerals indicate the same bones as in Tab. I. 13, 13. Vomer. 20. Palatine. 22. Premaxillary. 24. Pterygoid. The following perishable parts are indicated by the impressions left on the bone : Sn . The sincipital scute. . The inter-occipital scute. . The occipital scute. . The occipito-lateral scute. . The parietal scute. . The supraorbital scute. . The frontonasal scute. The frontal scute. ~< | = TIM. { : r dchart del. Dirkel iith TAB. IV. Chelone longiceps, nat. size. Fig. 1. Skull and portion of carapace. s2. Second neural plate. s3. Third neural plate. 2. Portion of carapace. s4—s11. Fourth to eleventh neural plates. pls5—plg. Impressions or remains of costal plates. v4—v5. Impressions of fourth and fifth vertebral scutes. TV. " Son ith to He Oueen, ante toute silt to el ne Pee a : 7 — » + > " ~ ro on - - a piadie owe notre Todltote to acitente; of Io seaby wha) oS Pe peels 4 a : a + : j we 7 > t. 7 bur Fee ck hag r ° Pee one) ie ; ‘| TAB. V. Chelone longiceps. Fig. 1. Upper view of the carapace, two thirds of the natural size. ch. Nuchal plates. si—s10. Neural plates. pli—ypls. Costal plates. vj—v4. Vertebral scutes. 2. Under view of the plastron of another specimen, two thirds nat. size. s. Entosternal. es. Episternals. hs. Hyosternals. ps. Hyposternals. xs. Xiphisternals. 63. The ischium. TAB. VI. Chelone latiscutata, nat. size. Fig. 1. Upper surface of the carapace. sl]. First neural plate. pli. First costal plate. s2. Second do. plz. Second do. 83. Third do. plz. Third do. s4. Fourth do. pls. Fourth do. s5. Fifth do. pls. Fifth do. s6. Sixth do. plé. Sixth do. v2. The impression of the second vertebral scute. v3. The impression of the third vertebral scute. 2. Lower surface of the plastron. s. Extremity of the entosternal. hs. The hyosternal. ps. The hyposternal. xs. Impressions of the xiphisternals. 3. Anterior surface of the carapace and plastron, showing the degree of convexity of those parts, and the depth of the osseous case. 51 is the scapular arch. ME. i DPrikel delet lth om sy J ph ibe PROVO ES Stes Z i Baie Avi) 4 a TAB, VII, Chelone convexa. Fig. 1. Upper view of the carapace, nat. size. 2. Under view of the plastron, nat. size. The letters and figures indicate the same parts as in the previous subjects. 53. The humerus. 64. The pubis. 65. The femur. 3. Under view of the symphysis and part of the rami of the lower jaw. 4. Outline of the curve of the carapace. T VIL Linkel del et lth a > Saat i 3 ‘ Fi we. ark eee Bf P el wil , TAB. VIII. Chelone subcristata. Fig. 5 1. Upper view of the carapace, three fifths of the natural size. 2. Under view of the plastron of the same specimen. The letters and figures indicate the same parts as in the preceding subjects. VIIT. r 7 TAB. VIII. Chelone subcarinata. Fig. 1. Upper view of the carapace, seven twelfths of the natural size. 2. Under view of the plastron of the same specimen. 3. Outline of the transverse contour of the carapace. VIA. . TAB, IX: Skull of Chelone planimentum, nat. size. Fig. 1. Under view of the lower jaw, showing the characteristic extent and flatness of the symphysis. 2. Upper view of the skull. 3. Side view of the skull. Tithonat trom Nature by GScharf Hulbnandel’s Pru TAB. X. Chelone planimentum. Under or inside view of the carapace, half the natural size. s5—ss. The fifth to the eighth neural plates which are anchylosed to the neural spines. sg—si1. Three succeeding neural plates which do not become so anchylosed. k go). ed lily Dink ° del Schar/ ‘ TAB. X24. Chelone planimentum. View of a cast of the under or inner surface of the carapace ; with portions of the ribs and marginal plates: one third the natural size. pli—pls. Impressions of the costal plates and ribs. mi, mi2. The eleventh and twelfth marginal plates. KC. TAB. XI. Skull of the Chelone crassicostata, two thirds of the nat. size. Fig. 1. Upper view, showing chiefly a cast of the under surface of the bones. 12. The situation of the postfrontals. 14. The prefrontals. 15. The nasals. 2. Side view. 3. Under view of the symphysis menti. PXL Diy £ Son lil to the Queen ler 0 italy ebro ih Ba arity Vue. TAB. XII. Chelone crassicostata. View of the inner surface of the carapace, half the natural size. ch. The nuchal plate. pli. ple. pls. pla. pls. pl. plz. pls. The first costal plate and adherent rib. The second ditto. The third ditto. The fourth ditto. The fifth ditto. The sixth ditto. The seventh ditto. The eighth ditto. The figures are placed above the free projecting ends of the ribs; they belong to the second and the ninth dorsal vertebre inclusive. sg. The ninth neural plate. sid. The tenth neural plate. py. The last neural or the “ pygal” plate. These are developed, like the nuchal plate, in the substance of the derm, and do not become confluent with any parts of the endoskeleton. Thindend del. & ith Day £. Son, lth "ta the Qacen T. XU. TAB: Xf. Chelone crassicostata. Fig. 1. Portion of the plastron seen from the under side. hs. The hyosternal; ps, the hyposternal; as, the xiphisternal. 52 is the coracoid, exposed by the removal of the right hyosternal. 2. Cast in the matrix of a portion of the carapace of the same individual, showing the characteristic thickness of the ribs, p/, pl. 7X. Day # Son. ith" to The Queen Dinkel delet litte = 1 5 i Sees TON rath 3 = ; >= Fi a lato ylieeeiod TAB. XII. Chelone crassicostata. Portion of the carapace, half the nat. size, with the corresponding series of marginal plates. #6—m12, and py. pl3 and pla, the third and fourth costal plates of the left side ; y/s—p/s, impres- sions in the matrix of the succeeding costal plates. T. XITA TAB. XIILB. Chelone crassicostata, half the nat. size. Fig. 1. Outside view of the carapace. s7—s10, the seventh to the tenth neural plates inclusive : pl2a—pls, the second to the eighth costal plates of the left side ; pl3—ypis, the third to the eighth, inclusive of the right side. 2. The plastron dislocated and crushed in, with part of the skull showing the orbit o ; hs, the hyosternal ; ps, the hyposternal ; 2s, the xiphisternal ; 51, the scapula ; * 52, the coracoid. rom Nature & on Stone by J Hrxleben. Pay kSenLi fu ; 2 : - right ma oft Fig. TAB. XiV. Chelone declivis. 1. Upper view of the left moiety of the carapace, nat. size. ch. 81. 82. §3. 84. 85. S6. 87. v1. v2. v3. VA. Impression of the nuchal plate. First neural plate. Second ditto. Third ditto. Fourth ditto. Fifth ditto. Sixth ditto. Seventh ditto. Impression of the first vertebral scute. pl. pl. pls. pla. pls. pl. plz. Impression of the second vertebral scute. Impression of the third vertebral scute. Impression of the fourth vertebral scute. First costal plate. Second ditto. Third ditto: Fourth ditto. Fifth ditto. Sixth ditto. Seventh ditto. 2. View of part of the dislocated right half of the carapace. The same letters and numerals signify the same parts. 5. Outline of the natural transverse curve of the carapace. LATE, Piers, rence 5 hat, Pal, Dayk.son, Luh tothe Queen Denkel dal. ob lath, TAB. XV. Skull of Chelone cuneiceps, nat. size. Fig. 1. Side view. 2. Top view. 3. Base view. 4. Back view. The letters and numerals indicate the same parts as in Tabs. I and III. TAMA Day i Son lth “to the Oncen Mnkel del. ck th ; Fig. . Upper view of the carapace, wanting the nuchal plate, half nat. size. TAB. XVI. Trionyx Henricr. si—s7. The first to the seventh neural plates inclusive. pii—pls. The eight costal plates of the left side. . Outline of the transverse curvature of the upper surface of the carapace. . The nuchal plate of probably the same species of Zrionyw; but of another individual: half the natural size. ELXYVE. Serer ene 3 EE aes Safes wil On Line hy | Erxteben TAB. XVI. The carapace of the Trionyx Barbara, half nat. size. a, Shows the longitudinal contour of the middle of the upper surface, and fig. 2, the transverse curvature of the carapace. TXVI-AS Nature on Stone by J Erxteben Day & Son. tith to the Qucen ¥ = ae : f i ee ~ Date Anas rhc sem, ike? i ol d ‘} ats Wee Lest 1 i é aa q e5umme nel : ; at tA. ryehal R faa rin tein ee Rte *. Me ‘Seve age itt % ~? tis plies, fit. seri “WT ARBCR roth ' ‘ ae, i ~' TAB. XVII. Trionyx incrassatus. Fig. 1. Inside view of the carapace, wanting the nuchal plate, half nat. size. s1—s7. The first to the seventh neural plates, with the connate neural spines and arches. pli—pls. The eight costal plates of the right side. cl. The place of attachment of the outer end of the first dorsal rib. c2—g. The portions of the consecutive dorsal ribs that become connate with the costal plates. 2. Transverse contour of the upper surface of the carapace. TF. XVI. 2Nat StZe. nd Fabhika dine E a | nae " a 5 a ae Ul < a ays » RE x Sy ; ie ’ \ , as Sis i © ne he. 7 ee oS eh ct 7 ‘ eotnle;? eo - oe ae 7 ‘ : FS. ; _ pyr oie “ rc ~ a oa ys ot = ‘ aA: s* moat f Pu wii? ititve i ’ TAB. XVIII. Trionyx incrassatus. Fig. 1. Upper or outside view of the fore part of the carapace with the nuchal plate, half nat. size. ch. The nuchal plate. sl. The first neural plate. s2. The second neural plate. phi—pls. The three anterior costal plates of the left side. 2. Under or inside view of the same specimen. ch. The nuchal plate. sl. The first neural plate connate with the neural spine of the second dorsal vertebra, of which part of the under surface of the centrum is here preserved and shown. s2. The second neural plate, with the connate neural arch of the third dorsal vertebra. pli—pl3. The three anterior costal plates of the right side. cl. The place of attachment of the outer end of the first dorsal rib. c2. The portion of the second dorsal rib that becomes connate with the first costal plate. 2’. The extremity of the rib that again becomes free. c3. The third rib attached to the second costal plate. c4. The fourth rib attached to the third costal plate. T XV pages Se renra svi ’ a -i4 a pla E ; . ani ey) 7 br pate sy) , ; ‘ hiedt Hinde sa) RAW Hrinnee FouteMosi in a) aie atl) A} ete wa ae ee ¥ F re : . : = 6) ee eAls - Pe ~ ee : Py “ so Sa Pape tric ie SHS ie eis a ~ * SA ; . a ~ - - ; s . . . * =e) oe TAB. XVIIIZ. Trionyx rivosus. Fig. 1. Outside view of hinder half of the carapace, nat. size. pla—pls. The fourth to the eighth costal plates inclusive. 2. Inside view-of the same specimen. pls—pls. The fourth to the eighth costal plates inclusive. 5—9. The ribs (fifth to the ninth dorsal inclusive) connate with the above costal plates. s6. The neural arch confluent with the sixth neural plate. TXVUL A. Day k Son lth" to the Queew From Nature on. Stone by J Tirxleben ion? os 4) i Matai geet io nim oo oe . 9 abe Da Pee. tee wo = “ble “fbi ‘ang yl lonlesene) sit) lik bune te igi te giet aa hay he RANT vt rn : di ' ok yc re : ata er Ave - , t r ro iy 4 gi - 2 i wor 7 i ea 4 ‘Yas sty STM. Seu i Fa) Ph ch Oth Weal? Owe _ “_y sta se) aaa ee SOT 1 vty ese te 4 eee Sale "hegpir gwd Pe ia it Jaleo ott aa th are A = i. . : ~s ee cs a BOT Pe es ae ay YE ht vr? lh mM ta orn nalunlite Revue BO? 1 f 1 ») Rie ee UL ind | - hii ed enyogerye wit," si {ONS UT aera Orit rz): ie * 7. ~~ eee are a hs = po slfwul oth Sheeley oe.y die tt a ele ie TABAKIX, Trionyx incrassatus. The parts are figured half the nat. size. 1. Entosternal. 2. Episternal, under side. 2’. Ditto. ubper side. 3. Part of right hyosternal, and the hyposternal, under or outer side. 3. hs, Ditto, and ps, ditto, upper side. 4. Two views of the scapula (51), and connate acromial clavicle (58) ; 4” shows the osseous structure of the end of the scapula, nat. size. The coracoid. , 6’. Two views of the ilium. , 7. Two views of the femur. , 8. Two views of an ungual phalanx, nat. size. . Under view of the sixth cervical vertebra ; y, y, the hypapophyses. . Upper view of the same vertebra; c, the anterior convex articular surface of the centrum; z, the neural arch; 2, 2, the zygapophyses (oblique or articular processes). . 9”. Back view of the same vertebra, showing the double concavity of the articular surface. oO DN S& & Jos Linkel dei. et. bith. k Nat. size. @e Deh ere|: TAB. XIX>. Trionyx marginatus. Fig. 1. Upper view of the carapace, wanting the nuchal plate, half the nat. size. letters and figures indicate the same parts as in Tab. XVI. 2. Outline of the transverse curvatures of the upper surface of the carapace. The TX Na i EE —— rea See COANAunA WD TAB. XIXB. . Upper surface of the third costal plate, right side, of the Zrionyx circumsulcatus, nat. size. . Articular margin of ditto; showing the natural curve and thickness of the plate. . Peripheral margin of ditto; showing the groove. Upper surface of the third costal plate, right side, of the Zrionya marginatus. . Sutural margin of ditto. Peripheral margin of ditto. Upper surface of a fragment of a costal plate of the Zrionyx pustulatus, nat. size. . Under surface of ditto, showing the large and prominent adherent rib. . Peripheral margin of ditto. TXIXB. Eraleben ni. Wadire Fr TAB. XIXC. Trionyx planus. Fig. 1. Upper view of the hind part of the carapace, half the nat. size. 2. Inside view of the same specimen ; p/5—yis, the fifth to the eighth costal plates inclusive. 8. Peripheral border of the fifth costal plate, nat. size. 4. Peripheral border of the fifth costal plate of the Zronyr Barbare, showing the difference in their relative thickness. LXIX.C. = ee eee —_ | ) TAB. XIXD. Under view of the lower jaw of a turtle (Chelone), nat. size. (Hordwell Cliff). Upper view of the same specimen. | . Upper view of the fourth cervical vertebra of a Zrionyx; d, diapophysis. Nat. size. . Side view of the same specimen (Hordwell Cliff). . The left os pubis of a Zrzonyx, nat. size (Hordwell Cliff). . Part of the plastron of Zrionyx planus, half the nat. size; 4s, hyosternal; ps, hyposternal. . Right hyposternal of a Zrionyz, from Bracklesham, half the nat. size. (In the Collection of Frederick Dixon, Esq., F.G.S.) LXE: —— a a eee Lay k Son lith to the Queen JS Lireleben tone by ¢ v Di TAB. XX. Emys Comptoni, nat. size. . Upper view of the carapace. . Under view of the plastron. . Side view, showing the marginal plates, m4—w7. . Front view. Back view. del. ek ith LXX. TAB. XXI. Platemys Bullockii, half the nat. size. The plastron and some of the marginal plates, @ a. &. es. Entosternal. Episternals. . Hyosternals. . Hyposternals. . Xiphisternals. . Intergular scute. Gular scutes. . Humeral scutes. - Pectoral scutes. . Abdominal scutes. The impression between these and the pectoral scutes crosses the intercalated supernumerary bones between the hyosternals and hyposternals. . Femoral scutes. an. Anal scute. Where the bones or scutes are in pairs, the figures or letters are placed on one of each pair. te ay F er oth a th TAB. XXII. Emys levis, two thirds the nat. size. Fig. 1. Upper view of carapace. 2. Under view of plastron. 3. Side view 4. Front view, showing the curvature and depth of the specimen. The letters and figures signify the same parts as in the preceding figures; /p, the accessory pieces of the plastron. $s ae 6. = ee ay = a A geek 3 , -- 5 ante Set nily Sead. Wye ryt’ aries oad a ae Gh Ah Sirt> af} bTKG © - TAB. XXIII. Platemys Bowerbankii, half the nat. size. Fig. 1. The mutilated carapace. 2. The plastron. The letters and figures indicate the same parts as in the preceding Table. 4 . az oy” er bile vor! enti ‘ VE bodwoibni c= < TAB. OXY. Emys testudiniformis, nat. size. Fig. 1. Nuchal plate. 2. Upper surface of the third neural plate. 3. Under surface of ditto. 4. Upper surface of the fifth neural plate. 5. A posterior marginal plate. 6. Front view of a mutilated cuirass in which the carapace has been slightly depressed; the natural curve, across the middle, is indicated by the outline. TAXI . aS ain Mueen Ze Day ki Son, lith”™ lo U Pinkel, del eb tith TAB. XXY. Emys bicarinata, two fifths the nat. size. The letters and numbers on the carapace, the upper surface of which is figured, indicate the same parts as in the previous figures. The transverse contour of the carapace is given in outline above. T XXY. ‘ 73 Natl. .Size TAB. XXVI. Emys ‘icarinata, two fifths the nat. size. The plastron ; s, the entosternal piece. xs, the xiphisternals. TAX VE “3 Nat. suze TAB. XXVII. Emys crassus, two thirds the nat. size. Fig. 1. Outside view of the left hyposternal. l’. Inside view of ditto. 2. Outside view of right hyosternal. 2’. Inside view of ditto. 3. Sutural border of hyosternal, nat. size. LD XXVIL. Nat. Sze. Linke, del. et lit Day t.Son,lith othe Queen TAB. XXVIII. Emys Delabechit, two fifths the nat. size. Upper or outside view of the carapace; the transverse curve is given in the outline ~ above. pli—pls. The eight costal plates of the left side. v2—v4. The second to the fourth vertebral scutes inclusive. Ys Nal. Six. igh Singin mnhenl ad isl cla T.XXVIM . AV ke Uh v TAB. XXIX. CHELONIA. Fig. 1. Side view of the fore part of the skull of the Platemys Bowerbanku, nat. size. 2. Upper view of the same fossil. 3. Side view of a fractured tympanic bone of a large Turtle (Chelone), from Brackle- sham, showing the long and slender ossicle or ‘ columella’ (16) 2” situ ; nat. size. 4. Extremity of the same tympanic bone, to which the ‘membrana tympani’ was attached. 5. Proximal end of the femur of a very large Chelonian from the Isle of Sheppy, nat. size. . 5. Left femur of a Turtle (Chelone mydas) which weighed 150 lbs., nat. size. J Nrxleben Daye Ser tith 19 the Oi 7 sais 24 us = iii 007 1872 CALIF ACAD OF $ i | nD ae eee te i