758 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.xxiv. 
Whatever ma}^ have been the history of the animal there can be 
little doubt that it is now a distinct species. I am inclined to believe 
that it was introduced b}' human ag-ency, but at a time far anterior to 
the estal)lishment of European trade. 
Genus MUS Linnaeus. 
Three species of Mus have been recorded from the Andaman Islands, 
Mus 7m1.sGu.lifs and 3his andamanensis by Blyth, and Mus Ixyuiersl by 
Blanford. Only the second of these was certain 1}^ obtained by Dr. 
Abbott, though it is probable that the animal here described as Mus 
taciturnus is the Mus howersi of Blanford. From the Nicobars the 
only rat hitherto known is the 3Ius j)almaruiR of Zelebor. This was 
regarded by Blanford as identical with Mus rattus. Dr. Abbott did 
not meet with it. On the other hand he secured six species in the 
Andamans and five in the Nicobars, raising the total number known 
from the islands to twelve. These may l)e distinguished by the fol- 
lowing characters: 
KEY TO THE SPECIES OP MUS KNOWN TO OCCUR ON THE ANDAMAN AND NICOBAR 
ISLANDS. 
Total length of adult less than 300 mm Mus viusciilm 
"^otal length of adult more than 300 mm. 
Greatest length of skull about 55 mm. 
Underparts yellowish white 3his palmarum 
Underparts brownish gray or bluish gray. 
Underparts strongly tinged with yellow Mus taciturnus 
Underparts slightly tinged with yellow Mus stoicus 
Greatest length of skull less than 50 mm. 
Fur distinctly spiny. 
Hind foot about 40 mm Musflehilis 
Hind foot distinctly less than 40 mm. 
Underparts whitish; skull with dorsal outline strongly convex. 
Mas andamanensis 
Underparts brown; skull with dorsal outline nearly straight. 
Mus puUiventer 
Fur soft. 
Back conspicuously blackish Mus atratus 
Back not blackish. 
Hind foot 40 mm. or more. 
Nasal bones abruptly constricted near middle Mas hurrescens 
Nasal bones not aljruptly consticted near middle . . Mus hurras 
Hind foot distinctly less than 40 mm. 
Back strongly tinged with dull red Mas hurralus 
Back yellowish brown. 
Color of belly sharply defined, teeth robust. 
Mus andamanensis 
Color of belly merging into that of sides, teeth weak. 
Mus alexandnnus 
