MUS. 407 



produced. Lower portion of anterior border to zygomatic process 

 of maxillary vertical, or slanting upwards and forwards, above 

 rounded off to a deep emargination. Lower part of infraorbital 

 foramen narrow, with a swelling in front on the maxillary bone. 

 The fronto-parietal area pyrit'orm, the low crest bordering the 

 parietal region convex throughout. Incisors narrow ; first upper 

 molar much larger than the second, which is nearly double the 

 size of the third. . 



Colour above in Indian specimens usually brown, more or less 

 rufous or occasionally yellowish brown ; more rarely blackish brown 

 or black ; below generally white, frequently sullied, sometimes 

 brown or grey and occasionally with a white, fulvous, or grey median 

 band. Basal three fourths of the dorsal hairs dark grey, the ter- 

 minal fourth mostly light brown, mixed with longer black tips. 

 When spines are present they are whitish near the base. Tail 

 generally the same colour throughout, but sometimes paler beneath. 

 Feet generally white. Incisors orange. 



Dimensions. Head and body 5 to 8 inches, tail 5 to 9 or even 

 more, hind foot without claws 1*2 to 1*5 ear P 7 to 1. An average 

 skull is 1-5 long by 0-75 broad. 



Distribution. Almost world-wide, doubtless from being intro- 

 duced. Probably indigenous in India and found throughout the 

 country, also in Burma and Ceylon, from the sea-level to ah eleva- 

 tion of at least 8000 feet. 



Varieties. The typical Mus rattus of Europe, the black rat, is 

 doubtless an introduced form. This variety is occasionally found 

 in various parts of India, chiefly large ports, whither it has probably 

 been brought by shipping. Besides this there are three Indian 

 varieties requiring notice : 



1. M. alexandrinus. Size generally large ; colour above brown 

 without much rufous tinge, below usually white. The tail is 

 longer than the head and body. This form is found in Western 

 India and extends thence to Northern Africa. Some specimens 

 from Simla have the under surface of the tail quite white. 



2. Mus nitidus.This differs from the last in having finer fur 

 often mixed with numerous spines, and in the tail differing 

 but little in length from the head and body, being sometimes 

 rather longer, sometimes a little shorter. Soles of feet often 

 white. The common Eastern Himalayan form. 



3. Mus rufescens. A more slender and frequently smaller 

 variety, with a long tail, generally spinous hair, and a rufous 

 or yellowish-brown tint. The variety chiefly found in the 

 Indian Peninsula, Ceylon, and Burma. More arboreal than 

 the others. 



Thomas, from whom I take most of these details, has shown that 

 the length of the nasal bones varies in specimens from one locality 

 from 46 to 69 per cent, of the length of the skull. 



Mus infralineatus was founded on a small short-tailed specimen 

 with a dark median line on the chest ; Mus andamanensis on a very 

 spiny variety (I have examined the type) ? and Mus yunnanensis on 



