32 
FASCICULI MAL AT FUSES 
It has been found impossible to divide these species into groups of equal 
value. In the case of the Jerdoni^ Whiteheadi^ XanthuruSy and Rattus sections, 
these groups are so subdivided as to have become, for practical purposes, of 
almost generic value, although showing no characters of sufficient importance 
to enable them to be generically separated. The remainder are groups of 
slightly superspecific value, and equal to the subgroups of the more variable 
forms. 
JERDONI GROUP 
Moderate sized to large rats ; fur as a rule thickly beset with spines. Colour above, brown 
or ochraceous, sharply marked off from pure white under parts. Tail long and generally bicolor. 
WHITEHEADI GROUP 
Similar to above but tail short, and the species all of moderate size. Colour of upper parts 
not sharply divided from that of lower parts, which are generally of a buffy white. 
XANTHURUS GROUP 
Large, soft-furred rats of brownish colour above, not sharply divided from that of the under 
parts, which are lighter in colour, sometimes white. The tail is of moderate length, naked, and 
its terminal portion white. 
MUELLERI GROUP 
Large grizzled rats with long black tail. Under parts white. 
BOWERSI GROUP 
Large rats of a silvery or brownish-grey colour minutely flecked with white. Tail long, 
unicolor. 
RATTUS GROUP 
The large and difficult group of Mus rattus, I propose, dealing only with Oriental specimens, 
to divide into three subgroups, viz. : — Rufescens, Pyctoris, and Griseiventer. 
{a) Subgroup Rufescens 
Hairs long, light coloured and yellowish, especially along the flanks, interspersed with longer 
black ones down the centre of the back. Ears large. Under parts white or yellowish-white. 
Tail slightly longer than head and body. Average measurements : — Head and body, 170 mm. ; 
Tail, 184 mm. ; Hind feet, 32 mm. ; Ear, 24 mm. A tree rat. 
{h) Subgroup Pyctorisi 
Hair moderately long and soft ; much darker and more uniform above than rufescens. 
Under parts white. Tail bearing about the same proportion to the head and body as in the 
former subgroup, possibly rather shorter. Whole animal smaller, especially the ear. Average 
measurements : — Head and body, 145 mm. ; Tail, 165 mm. ; Hind feet, 30 mm. ; 
Ear, 21 mm. A hill rat. 
I. This is the nitidus group of Thomas and various authors ; Mus nitidus belongs to my third subgroup, which 
I have called grisei'venter to save confusion. The types of both and nitidus are in the British Museum. 
