X PREFACE. 



Museum in Jermyn Street ; and the same privilege has been most kindly renewed by his 

 distinguished successor, Sir Roderick I. Murchison, to whom I beg to tender my warmest 

 acknowledgments. I am under many obligations to my friend Mr. Waterhouse, of the 

 British Museum, for his kindness in allowing me to examine all the Echinoderms in the 

 National Collection, and his permission to figure those I have selected for this purpose- 

 Professor Sedgwick, of Cambridge University, at my request, most liberally communicated 

 the types of Professor M'Coy's new species of urchins, described in the 'Annals of Natural 

 History.' Mr. Rupert Jones has at all times given me free admission to examine the rich 

 cabinets of the Geological Society of London. Professor PhiUips, of Oxford, has afforded 

 me much useful information relative to the species of Echinoderms first figured in his 

 valuable work on the ' Geology of Yorkshire.' To each of these kind friends I beg to 

 tender my most grateful acknowledgments. 



My best thanks are hkewise especially due to Messrs. Bone and Baily, for the great 

 care they have bestowed on the beautiful plates that enrich my Monograph, which, for 

 scientific accuracy in details, and artistic effect in execution, are second to no lithographs 

 of similar objects extant. 



THOMAS WRIGHT. 



Exeter Place, Cheltenham ; 

 August, 1856. 



