INTRODUCTION. 



This volume contains the descriptions of 151 species of Mar- 

 supials and 3 of Monotremata, in addition to 12 recognizable 

 varieties of the former and 2 of the latter, ma,king a total of 168 

 definable forms. The last general work on the subject (that of 

 Mr. G. E. Waterhouse, published in 1846) contained 120 species ; 

 but of these a certain number have since proved to be invalid, the 

 increase of species known being therefore rather greater than 

 appears at first sight. Of the 168, only 20 are not represented 

 in tha, British Museum collection. The specimens enumerated 

 amount to 1240 Marsupials and 64 Monotreme^s, making 1304 in aU, 

 a number that would be increased by at least one-half were the old 

 method adopted of counting the skin and the separated skull of the 

 same individual as two specimens. Of this total, 173 are preserved 

 whole in spirits, while the osteological collection of skeletons and 

 skulls, both separate and belonging to skins in the Museum, 

 amounts to 703. 



In the ' List of the Mammalia in the British Museum,' pub- 

 lished in 1843, 343 Marsupials and Monotremes are enumerated, 

 referred to 94 species ; and in the ' Catalogue of the Bones of 

 Mammalia,' issued in 1862, 331 skulls and skeletons are referred to, 

 a number less than one-half the present total. 



Apart from the mere number of specimens, however, as the 

 value of zoological collections depends so largely upon their posses- 

 sion of type specimens, the following table showing the distribution 



