1888.] MR, O. THOMAS ON A NEW RAT FROM NEW GUINEA. 237 



the contrary, in my specimen, comparatively large (especially so 

 upon the left side, c.a, fig. 5) — relatively larger, in fact, than in the 

 healthy individnal of the Common Frog prior to hibernation. In 

 consideration of all the facts, I think it probable that Espada was 

 mistaken, and that this extraordinary paternal instinct does not lead 

 up to that self-abnegation which he supposed. 



3. Description of a new Genus and Species of Rat from 

 New Guinea. By Oldfield Thomas. 



[Eeceived March 27, 1888.] 



Among the collections recently brought from New Guinea by Mr. 

 H. O. Forbes there occurs a specimen of Eat strongly resembling, 

 superficially, the common small Papuan Uromys, U. cervinipes, 

 Gould, but showing on a closer examination such characters, both 

 external and cranial, as to necessitate the formation of a special 

 genus for its reception : of these characters by far the most striking 

 is its possession of a tail modified for prehension in the same fashion ^, 

 and almost to the same extent, as in the Phalangers inhabiting the 

 same country. Among the other members of the Myomorpha, so 

 far as I know, the only ones that have a truly prehensile tail are 

 Dendromys and the common Harvest-Mouse {Mus minutus), in each 

 of which there is a tendency towards the same modification of the tail 

 as in the present animal. Otherwise, among the whole of the 

 Rodents, this character is only found in the South-American Porcu- 

 pines. It is true that many other Rats and Mice have the power 

 of twisting their tails round branches, and so helping themselves in 

 climbing, but in none is this so far developed as to cause any 

 important modification in the actual structure of the tail, as is the 

 case in the animal now described. 



The teeth, again, are remarkably complicated, and show a high 

 degree of specialization, far more than is found in any other genus 

 at all allied to the present one. This extreme specialization both 

 of teeth and tail is especially remarkable in an animal inhabiting 

 such a refuge for old and litile-modified forms as New Guinea. 



The following is a detailed description of the new form : — 



Chiruromys, g. n. 



Externally like Mus, but with the terminal portion of the tail above 

 without scales, quite naked, transversely wrinkled, and obviously 

 prehensile. Scales of rest of tail (fig. 2, c) not, as is usual, square 

 and arranged in distinct rings, but more or less pentagonal or lozenge- 

 shaped, and set in diagonal slanting series, somewhat like the dorsal 

 scales of a snake. 



Skull (fig. 1, p. 238) with the infraorbital foramen typical in shape, 

 but with its external wall narrow and not produced forwards as a 

 projecting plate. Anterior part of zygomata projecting outwards 



' Except that the curl is upwards instead of downwards. 

 Proc. Zool. Soc— 1888, No. XVII. 17 



