FASCICULI MALATENSES 
37 
Whiteheadi group. M. whiteheadi and M. asper are very closely allied. M. ochraceiventer 
is larger, has deep ochraceous under parts, and is much darker above. Mus alticola is dark brown 
above, showing no trace of the fulvous tint ; the under parts are dull white. 
M. baeodon is considerably smaller than M. whiteheadi, and has whitish under parts ; it also 
differs in its cranial characters. With the exception of M. musschenbroeki, they are all spiny. 
Bowersi group. The two specimens from the Hume Collection referred by Mr. Thomas 
{P.Z.S. 1886, p. 62), to Mus berdmorei, Blyth, resemble Mus bowersi so closely, except in size, that 
I have no hesitation in placing them in the same group. The hind feet of M. berdmorei measures 
35 mm., and that of M. bowersi 52 mm. 
Xanthurus group. The differences between the various species have been tabulated by 
Mr. Thomas {P.Z.S. 1887, p. 573), who also, in his description of M. luzonicus, clearly 
distinguishes it from M. everetti. 
Muelleri group. This group are large dark coloured rats, with long uniformly black tails. 
They are all grizzled to a greater or less extent with fulvous ; the under parts are, in the case of 
M. validus, of a greyish-white, but in M. muelleri itself, yellowish-white. 
Mus infraluteus is a fine and distinct species, but allied to the above group in size and 
cranial characters. It is of a uniform very dark brown above, some of the hairs having light, 
glistening tips. Under parts with dark grey under fur, and long, light, glistening stiff hairs, of a 
spiny character. 
The divisions into which I have divided the rats of the MuS rattUS group are, to a large 
extent, correlated with the habits and situations in which they are found. Those of the Rufescens 
subgroup are tree rats, although in many places they may also be found in houses, and at 
considerable elevations as well. 
The Pyctoris subgroup contains hill rats which are not found in low lying land, and Mus 
grieiventer represents the true house rat, its chief characters being the large feet, correlated with 
short ears. The great difficulty to be contended with in this group is the fact of their travelling 
about on ships, with the result that many varieties and forms occur which cannot be definitely 
assigned to any of the subgroups, and this has caused a great number of these varieties to be 
described. One finds, however, as in the case of most small mammals, that in localities 
away from the direct influence of imported specimens, individuals from any one district are 
remarkably constant in their characters. In working out this group, reference should be made 
to the following sources : — 
Oldfield Thomas. P.Z.S. 1881, p. 521, etc. 
W. L. ScLATER. P.Z.S. 1890, p. 523. 
Cat. Mamm. Ind. Mus., p. 62 (1891). 
I have not gone into the Chinese forms of this group with the exception of M. flavipectus, 
which belongs to the Rufescens subgroup, differing therefrom only in having the under parts 
suffused with buffish. 
M. vicerex, which I have recently described, is a very well-marked form of M. rufescens ; 
its main point of distinction lies in its bicolor tail, which is also well-clothed with moderately 
long hair. In colour it is a pale-grey form of M. rufescens, the long black hairs having a 
greenish gloss, which, although present in Rufescens, is not nearly so conspicuous a feature. 
Most of the specimens labelled M. nitidus in the Museum belong in reality to M. pyctoris, 
Hodgs., which is chiefly to be distinguished by its darker and warmer tints and its longer fur. 
