222 JOURNAL, NATURAL HIST. SOCIETY OF SIAM Vol. I. 
Under-surtace to the bases of the hairs, white, fairly clearly 
margined, and continuous down the thighs to the hind-feet which are 
conspicuously pale. Tail dark throughout. 
Skull and -Teeth. Hardly differ from those of mainland animal 
except that the cranium seems to be rather narrower or more pear- 
shaped, owing to the closer approximation of the. parietal ridges while 
the sides of the cranium are less vertical. | 
Measurements. ars of type, 24, of the series, 22-24 mm. 
Vor other measurements see table p. 223. 
Specimens ewumined. Thirteen, all from Koh Si Chang. 
Remarks. The light upper surface closely resembling in colour 
the back of some races of surifer rats markedly separates this form 
from the much darker, duller mainland animals. This bright back 
and the pure white under surface seem further to be present at all 
ages, as young individuals do not differ from adults. 
Epimys rattus poenitentiarii, subsp. nov. 
Type. Adult male (skin and skull) No. 1966/C. B, K. Collect- 
ed on Koh Phai, Inner Gulf of Siam, Ist February, 1915. 
Diagnosis. Colour like #. 7. portus but size rather smaller. 
Skull like that H. 7. portus but with bullae markedly smaller and less 
dilated than is the case both with it and with the mainland animal. 
Measurements. Ear of type 23, of series 21-23 mm. 
For other measurements see table p. 224. 
Specimens examined. Fifteen all from Koh Phai. 
Remarks. Besides being a rather less robust animal the cons- 
picuous difference in size and form of bullae compel separation of this 
animal from that of Koh Si Chang and the mainland. 
