PREFACE. 



The aims and objects of this Monograph are so fully 

 and lucidly described by the author in his Introduction 

 that it is unnecessary for me to attempt to re-state them. 

 The results of Dr. Boulenger's ripe experience, based as 

 they are on the examination of an enormous amount of 

 material, will certainly be of great value to his fellow- 

 workers in the same field. The Trustees of the British 

 Museum have already published a long series of impor- 

 tant Catalogues prepared by him, on Fishes and 

 Batrachians as well as on Reptiles ; and, on the eve 

 of his approaching retirement, they have informed him 

 of their high appreciation of the value of his services. 

 It remains to me to express my great regret that this 

 Monograph is the last which can be expected to be pro- 

 duced by him in his official capacity as a member of the 

 stall:'. 



The thanks of the Trustees are due to the numerous 

 donors of the specimens on which this work is largely 

 based, as well as to those who have lent specimens or 

 have assisted the author in any other way. The names 

 of the principal helpers are stated in the Introduction 

 and repeatedly in the text, while those of other donors 

 will be mentioned in the list of specimens which is to 

 appear at the end of the second and concluding volume. 



Sidney F. Hakmer, 

 Keeper of Zoologij. 



British Museum (Natural History), 

 London, S.W. 7. 



May, I'JL'U. 



