TRANSACTIONS OF THE GEOLOGICAL SOCIETY OF LONDON. SECOND SERIES. VOLUME VII. Quod si cui mortaliuxn cordi et cum sit, non tantnm inventis hserere, atque us uti, Bed ad ulteriora penetrare; atque non disputando adversaritnn, sed opere naturam vincere; denique non belle et proba- biliter opinari, sed certo et ostensive scire; tales, tanquam veri scientiarum filii, nobis (si videbitur) se adjungant. Novum Orgamm* Prmfatio. LONDON: PUBLISHED BY LONGMAN, BROWN, GREEN, AND LONGMANS. SOLD ALSO AT THE APARTMENTS OF THE GEOLOGICAL SOCIETY, SOMERSET HOUSE. 1845-1856, OFFICERS AND COUNCIL4 OF THE GEOLOGICAL SOCIETY OF LONDON. 1845. PRESIDENT. LEONARD HORNER, Esq., F.R.S. L. & E. VICE-PRESIDENTS. REV. PROF. BUCKLAND, D.D. R. 1. MURCHISON, Esq., F.R.S. L.S. ROBERT HUTTON, Esq., M.R.I.A. PROF. OWEN, F.R.S. L,S. SECRETARY. WILLIAM JOHN HAMILTON, Esq., M.P. FOREIGN SECRETARY. SIR H. T. DE LA BECHE, F.R.S. & L.S. TREASURER. JOHN LEWIS PREVOST, Esq. COUNCIL. ROBERT A. C. AUSTEN, Esq. G. B. GREENOUGH, Esq., F.R.S. L.S. CHARLES DARWIN, Esq., M.A., F.R.S. CHARLES LYELL, jun.,. Esq., M.A., F.R.S. L.S, SIR P. GREY EGERTON, Bart., M.P., F.R.S. MARQUESS OF NORTHAMPTON, Pres. R.S. LIEUT.-COL. EVEREST, F.R.S. SAMUEL PEACE PRATT, Esq., F.R.S. L.S. HUGH FALCONER, M.D., F.R.S. LIEUT.-COL. SABINE, R.A., F.R.S. WILLIAM HENRY FITTON, M.D., F.R.S. L.S. REV. PROF. SEDGWICK, F.R.S. PROF. EDWARD FORBES, F.R.S. L.S. HENRY WARBURTON, Esq., M.P., F.R.S. J. H. GREEN, Esq., F.R.S. VICE-SECRETARY. PROF. ANSTED, M.A., F.R.S. ADVERTISEMENT. THE Editors of the Transactions of the Geological Society are directed to make it known to the Public, that the Authors alone are responsible for the facts and opinions contained in their respective papers. It is requested that all letters and communications to the Secretaries, and presents to the Society, may be addressed to the Apartments of the Geological Society, Somerset House, London. OFFICERS AND COUNCIL OF THE GEOLOGICAL SOCIETY OF LONDON. 1856. PRESIDENT. DANIEL SHARPE, Esq., F.R.S. and L.S. VICE-PRESIDENTS. Sir P. de M. G. EGERTON, Bart., M.P., F.R.S. j Sir CHARLES LYELL, F.R.S. & L.S. R. A. GODWIN-AUSTEN, Esq., B.A., F.R.S. I Col. PORTLOCK, R.E., F.R.S. SECRETARIES. ROBERT W. MYLNE, Esq. | WARINGTON W. SMYTH, Esq., M.A. FOREIGN SECRETARY. SAMUEL PEACE PRATT, Esq., F.R.S. & L.S. TREASURER. JOSEPH PRESTWICH, Esq., F.R.S. COUNCIL. Prof. THOMAS BELL, F.R.S. & L.S. JOHN C. MOORE, Esq., M.A., F.R.S. Col. Sir P. T. CAUTLEY, K.C.B., F.R.S. & L.S. JOHN MORRIS, Esq. EARL OF DUCIE, F.R.S. Sir R. I. MURCHISON, G.C.St.S., F.R.S. & L.S. THOMAS F. GIBSON, Esq. S. R. PATTISON, Esq. WILLIAM JOHN HAMILTON, Esq., F.R.S. Prof. JOHN PHILLIPS, F.R.S. WILLIAM HOPKINS, Esq., M.A., F.R.S. Prof. A. C. RAMSAY, F.R.S. LEONARD HORNER, Esq., F.R.S.L. & E. HENRY CLIFTON SORBY, Esq. ASSISTANT-SECRETARY, CURATOR, AND LIBRARIAN. T. RUPERT JONES, Esq. ADVERTISEMENT. THE Editors of the Transactions of the Geological Society are directed to make it known to the Public, that the Authors alone are responsible for the facts and opinions contained in their respective papers. It is requested that all letters and communications to the Secretaries, and presents to the Society, may be addressed to the Apartments of the Geological Society, Somerset House, London. .