PKEFACE TO THE FOUETH EDITION. 
The alterations introduced into the present edition consist chiefly 
in changes of nomenclature, and in references to the more im- 
portant additions which have been placed on exhibition since the 
previous issue of this Guide : such as specimens of the Two-humped 
Camel of Central Asia, of the Pigmy Hippopotamus of Liberia, 
of a fullgrown ram of Hodgson^s Sheep ; skeletons of the Killer- 
Whale and Grey Whale of the North Pacific ; the recently 
discovered Mole-like Marsupial from Central Australia. The 
opening-up of the countries of Eastern and Central Africa has 
yielded several new and interesting forms of Antelope, whiJst 
Mr. St. G. Littledale has enriched the collection with a pair of 
the European Wild Bison, a series of Polo^s Sheep, and several 
other large game-animals, all obtained by himself during his 
expeditions into the Caucasus and Central Asia. Finally, The 
exhibition of heads and horns of big game will be found con- 
siderably enlarged by a magnificent donation of A. 0. Hume, 
Esq., C.B., who has presented to the Trustees the whole of his 
Collection of Indian Mammals. 
Zoological Department, 
July 3, 1892. 
A. G. 
