102 HYDROMYS. 
2. Hypromys FULvoLAvaTuSs, Gould (1863). 
Western Water Rat. 
General color of fur orange-buff or buffy-brown, but the 
numerous black hairs which are dispersed over the upper surface 
give those parts a dusky hue; the whiskers, which in the other 
species are entirely black, are in this mixed black and white , 
outer surface of limbs dark brown ; upper surface of hind limbs 
pale brown, deepening towards the toes ; nails white ; tail black, 
except the extreme tip which is white. 
Habitat.—South and West Australia, 
Reference.—Gould, Mamm. Austr. iii. pls. xxv.(H. fulvolavatus ) 
and xxvii. (H. fuliginosus ). 
Note.— As with its eastern representative there are two distinct 
color varieties of the Western Water Rat. Mr. Oldfield Thomas 
apparently considers (v. Proc. Zool. Soc., 1889, p. 247) all six 
described forms of //ydromys to belong to one and the same 
species. His words are as follows: ‘One of the most singular, 
and at the same time the most isolated genera of Murida is 
Hydromys, of which the on/y species is the well-known Australian 
Water-rat.” According to this H. chrysogaster is the name by 
which the sole species should be known. 
Genus II.—XEROMYS, Thomas (1889). 
External form murine. Tip of muzzle as in J/us, not as in 
Hydromys. Toes unwebbed. Tail scaly, very finely haired. 
Skull as in Mus, except that the supraorbital edges are rounded. 
teeth both in number and structure as in Hydromys. Infra- 
orbital foramen typically murine, the outer wall broad and 
slightly projecting forwards. 
Distribution.—Queensland. 
Dentition.—I. i M. : SI 
Habits.—Terrestrial. , 
1. XeRomys myoipEs, Z’homas (1889). 
Thomas’ Rat. 
External appearance like that of an ordinary Rat. Lars short 
and rounded, laid forward they only reach to within three or 
four millimetres of the posterior canthus of the eye; their 
anterior edge without the supplementary flap found in Hydromys. 
Fur very short, uniform in length. Whiskers as in J/ws, fewer 
and slenderer than in Hydromys. General color above dark 
slaty-gray, below white. Ears gray. Arms and legs like the 
back ; hands and feet very thinly haired, almost naked terminally, 
