XIV PREFACE. 



kindly transmitted to me the portions of the tooth of the great 

 Mastodonsaurus, or Labyrinthodon, from which the sections described 

 and figured in the present Work are taken. Dr. Lloyd of Leaming- 

 ton, liberally consented to sacrifice his specimens of the extremely 

 rare teeth of the English Labyrinthodonts, for the requisite com- 

 parison of their structure with that of the teeth of the more gigantic 

 species of the Wirtemberg Keuper Sandstones. To Alex. Robertson, 

 Esq., of Elgin, and R. I. Murchison, Esq., P.G.S., I owe the 

 opportunities of examining the teeth of the Dendrodus. Mr. George 

 Bennett of Sydney, and Dr. Hobson of Melbourne, have transmitted 

 to me the jaws and teeth of the rare Cestracion of the Australian 

 seas. Dr. Mantell has supplied me with the teeth of the Iguanodon 

 and Gyrodus. Dr. Buckland, Dr. Agassiz, Capt. Jones, R.N., 

 Charles Stokes, Esq., Fred. Dixon, Esq., of Worthing, J. C. Bower- 

 bank, Esq., and other friends and colleagues in the Geological 

 Society, have most liberally contributed subjects described in the 

 present Work. Messrs. Stokes, Bowerbank, and Lister, have also 

 kindly granted me the use of their valuable miscroscopes when- 

 ever I wished so to test or verify observations made with my own. 



My grateful acknowledgements are more especially due to the 

 President and Council of the Royal College of Surgeons : for 

 to them I owe the appointments which have made the pursuits 

 most congenial to my tastes a duty, and at the same time have 

 supplied the best means and opportunities of fulfilling it. In whatever 

 degree, therefore, I may have contributed in this or previous Works 

 to the advancement of Comparative Anatomy, or may have aided 

 in its application to collateral sciences, I can only regard myself as 

 instrumental, in such measure, in carrying, out the great objects 

 which the College of Surgeons had in view in accepting the 

 important trust of the Hunterian Museum, and which the College 

 has ever since most strenuously promoted. 



