64 MAMMALIA. 



The Black Rat or Tree Rat ; Bengalee, Gachua indur; Singa- 

 lese, Ghasmeeyo. 



Distribution. — The typical Black Rat is found all over Northern 

 Europe and Western Asia ; it has been, however, almost entirely 

 displaced by the Brown Rat (Mus decumanus) in England and on 

 those parts of the continent which are within easy access of the 

 sea ; it is also found in most of the seaport towns all over the 

 world, but here also the Brown Rat struggles for existance with it. 



The Alexandrine Rat (Mus rattus alexandrinus) is merely a south- 

 ern variety of the Black Rat, distinguished by its softer and reddish 

 or greyish fur, and usually by its white belly; it is found in south- 

 ern Europe, Egypt and Palestine and specimens identical with it 

 have been got from Gilgit. 



The Tree Rat (Mus rattus rufescens) is a smaller variety of the 

 Alexandrine Rat and is spread all over India, Ceylon, Assam and 

 Burma, extending as far south as Mergui at any rate. 



The Hill Rat (Mus rattus nitidus) is a rather short-tailed variety 

 which is found in Nepal and Sikkim only. 



The Andamanese variety of Mus rattus is distinguished from the 

 ordinary Mus rattus rufescens of India by its spiny fur, a character 

 which has been shown by Thomas not to be of even specific value, 

 and also by its slightly larger size as is shown by the following 

 measurements taken from the two original skins: — head and body: 

 7'io to 7"3o ; tail, 6'65 ; hind-foot, i"40 ; a typical Mus rattus jufes- 

 cens measures, head and body, 5'7o; tail, 670 ; hind-foot, vzo. 



No distinction except that of size can be found between the 

 skulls of the several varieties of Mus rattus, and it is often difficult 

 without a knowledge of the locality to say to which variety a 

 particular individual of this species should be referred so much do 

 they run into one another, 



S.B 



