PEEFACE. 



This volume, the greater part of whict is devoted to the Marsupialia, 

 has been prepared by Mr. 0. Thomas, one of the Assistants in this 

 Department, on the plan of the new series of the Zoological Cata- 

 logues of the British Museum ; it contains descriptions of every 

 species known, with references to all the descriptions and figures 

 previously published, and gives a complete detailed list of the 

 specimens in the Museum Collection. 



The large series of specimens examined by the author has enabled 

 him to pay special attention to the various degrees of relation which 

 obtain between forms previously described under uniformly binomial 

 terms ; in judging of these relationships he has relied on craniolo- 

 gioal as well as external characters. 



Beside the Marsupials the Monotremes have been embodied in this 

 volume, this division of Mammals being numerically too small to 

 form a volume by itself. 



Since the year 1843, when ' The List of Mammalia in the Col- 

 lection of the British Museum ' was prepared by my predecessor, no 

 general account of the Marsupials in that coUeotion has been pub- 

 lished, whilst nearly all the other Orders of the Class were made the 

 subjects of continuous study and revision. This seeming neglect 

 was chiefly duo to the appearance of two works, vii. Water- 

 house's standard work on these Mammals in 1846, which then, in 

 the course of the following twelve years, was supplemented by Gould's 

 excellent illustrations in his ' Mammals of Australia.' Both these 

 works had a direct relation to the collection of the British Museum, 

 and for many years seemed to fully satisfy the needs of the zoologist. 



