474 PHILIPPINE RODENTS CHAP. 
Sub-Fam. 2. Hydromyinae.—The genus Hydromys,' of which 
there are several species, the best known being H. chrysogaster, 
is an exclusively Australian form, and is aquatic in habit. It 
is a foot or so in length, and has a fairly long tail. The fore- 
and hind-limbs are webbed, in correspondence with its habits. 
The Australian Water-Rat is black, with an admixture of golden- 
coloured hairs dorsally and golden colour below, with a leghter 
median stripe. The thumb is small, and the webbing of the 
hands is not so marked as is that of the feet. The molars are 
only two in each half of each jaw. The caecum is rather small, 
the measurements of the alimentary canal being: small intestine, 
895 mm.; large intestine,278 mm.; caecum, 70 mm. Allied to 
the last is Xeromys, a genus which is also Australian, but hmited 
to Queensland. It has been established by Mr. Thomas,? who 
discovered that it has the same reduced formula as Hydromys. 
Xeromys, however, 1s not an aquatic animal, and has unwebbed 
feet. 
In the Luzon highlands Mr. Whitehead has discovered, and 
Mr. Thomas quite recently described,* a number of peculiar 
Rodents. Of these the genera Chrotomys, Celaenomys, and Cru- 
nomys are allied to the Australian and New Guinea Hydromys. 
Chrotomys whiteheadi is unusual among Muridae, in its 
coloration being marked by a pale stripe down the back. The 
creature is the size of the Black Rat (J/us rattus). It is terres- 
trial not aquatic in habit, in spite of its lkeness to Hydromys. 
The molars, however, are 3. 
Crunomys fallax is more like Hydromys. It has, however, 
three molars, as in the last genus. But the skull has the 
flattened form characteristic of Hydromys as opposed to Mus. 
Like Batomys, Celaenomys silaceus is also somewhat inter- 
mediate between Hydromys and Mus. It is described as very 
Shrew-like in appearance, and has a very pointed muzzle. Its 
habits Mr. Whitehead is “quite unable even to guess at.” Like 
Hydromys and Xeromys this Rodent has but two molars. 
Sub-Fam. 3. Rhynchomyinae.—The genus Rhynchomys, con- 
taining but one species, 21. soricioides (of Thomas), is also, as both 
its generic and specific names imply, a somewhat Shrew-like form in 
external aspect. The skull, too, is Insectivore-lke in its elonga- 
1 For anatomy see Windle, Proc. Zool. Soc. 1887, p. 53. 
2 Proc. Zool. Soc. 1889, p. 247. 3? Trans. Zool. Soc. xiv. 1898, p. 377. 
