248 MR. 0. THOMAS ON A NEW GENUS OF MURID2. [May 7, 
dentition, as both the cranial and external characters of the new 
genus are those of ordinary Muride. The new form, by its structure, 
is obviously a land- and not a water-animal, and on this account, 
in contradistinction to its aquatic ally Hydromys, I propose to call it 
Xeromys', g. n. 
External form murine. Tip of muzzle as in Mus, 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. 
XEROMYS MYOIDES, sp. n. 
External appearance exactly like that of an ordinary Mus. Size 
about twice that of Mus musculus. Ears short (as compared to most 
members of Mus), rounded, laid forward they only reach to within 
about 3 or 4 millim. of the posterior canthus of the eye; their anterior 
edge without the little supplementary flap found in Hydromys. 
Fur very short, uniform in length. Whiskers as in Mus, fewer and 
slenderer than in Hydromys. General colour above dark slaty grey, 
below white, the line of demareation not sharply defined. Ears 
grey. Arms and legs like back; hands and feet very thinly haired, 
almost naked terminally, white. Palms and soles (Plate XXIX. 
fig. 9) naked, the former with five and the latter with six pads, the 
last hind pad elongate. Pollex with a short broad nail, all the other 
digits with claws; fifth digit on each foot, without claw, reaching 
just to the base of the fourth. Tail about the length of the body 
without the head, slender, scaly, the scales rather irregularly disposed, 
very small, averaging about 20 to 22 to the centimetre, the whole 
tail very thinly covered with fine white hairs; its substance pale 
flesh-colour above and below. Palate-ridges exactly as in Hydromys, 
i. e. three predental, the third notched in its centre, three interrupted 
interdental ridges, and one posterior uninterrupted (see Plate XXIX. 
fig. 5). Mamme 0—2=4, as in Hydromys. 
Skull (Piate XXIX. figs. 1-4), in its general form, not unlike that 
of asmall Rat, say of the common N. Australian Uromys cervinipes, 
Gould. Nasals reaching much further forwards than in Hydromys, 
but not so far as in Mus, just falling short of the level of the front 
of the premaxillee. Interorbital region smoothly convex, the supra- 
orbital edges rounded, not ridged or beaded. Interparietal very 
broad transversely, and narrow antero-posteriorly. Infraorbital 
foramen typically murine in character, the outer wall broad and 
slightly projecting forwards (fig. 6). Anterior palatine foramina 
short, not eqnalling the combined length of the two upper molars. 
Bulle small, inflated, transparent. 
Teeth.— Upper incisors long, less curved than in Mus, and recalling 
in their general appearance those of the Voles. Their front surfaces 
smooth, ungrooved, orange in colour. Molars (Plate XXIX. fig. 10) 
as in Hydromys chrysogaster, except that the lateral ends of the 
lobes are shorter and rounder, and that the inner wall of the second 
1 Enpods, dry; 2) Enpa, the dry land. 
