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Show 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, ca, fig. 5)-relatively larger, in fact, than in the healthy individual 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 NTew Guinea. By OLDFIELD THOMAS. [Eeceived March 27, 1888.] Among the collections recently brought from New Guinea by Mr. H. 0. Forbes there occurs a specimen of Rat 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 Porcupines. 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 little-modified forms as N e w 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 1 Except that the curl is upwards instead of downwards. PROC. ZOOL. Soc-1888, No. XVII. 17 |
