940 OLDFIELD THOMAS 
soles, and 2—2=8 mammae. Within the group the specific 
distinctions are exceedingly vague and difficult to make out, 
depending for the most part nearly entirely on size and on 
the lengths of the tail and feet. The proper determination of 
Signor Fea’s specimens has therefore been by no means easy, 
and the present plan, by which all the specimens with hind- 
feet less than 35 millim. long are referred to M. jerdoni, 
and those in which that measurement ‘exceeds 37 millim. to 
M. coxingi, must be looked upon as provisional. In the series 
from Mt. Mooleyit the tails are usually wholly bicolor from 
base to tip as in typical Himalayan specimens of M. jerdoni, 
but sometimes the lower side of it is brown like the upper (+), 
a difference therefore that this series proves not to be so ab- 
solutely diagnostic as it has been usually supposed to be. On 
the other hand, in all the larger Thagata and Plapoo specimens 
here referred to M. coxingz, the tail is bicolor for its basal half 
and wholly white for its terminal half, very much as in Mus 
blanfordi (*). This character however is in all probability a me- 
rely local peculiarity, since Mr. Swinhoe’s original series from 
Formosa mostly have the tail uniformly bicolor, as in M. jerdonz. 
That it is not a character of specific importance is shown by 
to fact that the Paris Museum series of the closely allied Mus 
confucianus (3) contains specimens with both bicolor and white- 
tipped tails. Finally even if these Thagata and Plapoo rats turn 
out to be specifically distinct from M. coxingi there is yet ‘ano- 
ther closely allied form which may be found to grade into them, 
namely M. hellwaldi, Jent. (*) from Celebes, so that in any 
case it would not be safe to describe them as new. Rats of 
this type are also known from Sumatra, Java, Borneo and the 
Philippines, but it is at present impossible to say how many 
species they really form, and it may easily be that all the dif 
ferences now believed to exist between the described species 
(!) This only occurs in a few of the larger specimens, and may be due to age. 
(*) See P. Z. S., 1881, p. 542, pl. L. 
@) M. Edw. Rech. Mamm., p. 286, Atl. pl. XLI, fig. 2, 1884. 
(#) Notes Leyd. Mus. I, p. 8, 1878. 
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