The Atoll of Funafuti, Ellice group : its zoology, botany, ethnology and general structure based on collections made by Charles Hedley of the Australian Museum, Sydney, N.S.W.
Native Rat. — Mus Exulans, Peale
Mus Exulans, Peale.
Mus exulans, Peale, U.S. Expl. Exp., Mamm., 1st Ed., 1848, p. 47.
(Plate viii., figs. la-f.
Fur fine, scanty, and of medium length; colour warm brown, reddish on the nape and back, basal half of the hair delicate grey, the tips yellowish or brown. On the back the fur is mixed with longer and comparatively thick hairs of bristly texture, these are white or very pale yellow throughout their length, the extreme tip only being dark brown. Muzzle and face warm brown; the hairs on the sides of the body are tipped with pale yellow with no longer or darker hairs intermixed, The whole under surface including the inside of the limbs white, fur pale grey at the base. Ears rounded and of considerable breadth, but on being laid forward they do not reach the eye. Outside of limbs coloured like the back; on the hind foot the colour extends scarcely further than the heel leaving nearly all the foot white. Foot and claw-pads very large. Tail longer than the head and body, quite rat-like. Hairs longer than the scales, but not so long as two scales, excepting towards the tip which is inclined to be pencilled. Scales 9½ to the centimeter; mammae 2.2= 8.
Skull of delicate proportions; the nasals project considerably beyond the line of the premaxillary; supraorbital ridge thin but very prominent, it becomes lower in the temporal region and is little more than discernable above the aural aperture: condition of occipital region unknown. The anterior palatina foramina are somewhat broad and reach the anterior margin of the molar alveoli. The anterior zygoma root is rounded above and the front edge scarcely emarginate.page 175
Teeth.—The teeth do not call for special reference, the character of the molar pattern being sufficiently represented on the accompanying plate (fig. Id).
|Head and body||125·0|
|Length of head||37·5|
|Muzzle to ear||30·0|
|Forearm and hand||35·0|
|Heel to front of last foot-pad||13·7|
|Last foot pad||5·0|
|Nasals, greatest breadth||4·0||4·1|
|Anterior zygoma root||3·5||3·8|
|Anterior palatina foramina||5·7||6·0|
|Upper molars, length||5·7||6·2|
|Lower molars, length||6·0||?|
|Condyle to incisor tip||? 23·0||?|
|Coronoid tip to angle||9·2||?|
Peale18 states that in his examples "the females have two pectoral and four abdominal teats," whereas in mine the pectorals are four. This may be reconciled by supposing that Peale overlooked a pair of mammas, an error, as I have in a former article indicated, easily committed.
Three examples of the Funafuti native rat were included in the collection: two of these I had not the opportunity of examining. The third had the skull a little but not very seriously damaged, and fragments of a fourth specimen enabled me to add the few figures in the second column of skull dimensions.
The stomach of the rat examined contained a white vegetable substance, possibly cocoanut or pandanus.
On the Funafuti Atoll this rat is known to the inhabitants by the name of "Tikimoa."page 176
The Pacific Ocean being bounded by the land masses of Asia, Australia, South and North America, and the genus Mus being exclusively confined to the Old World, it necessarily follows that this rat has entered the islands of the Pacific from an Asiatic source. This agrees with the origin of the flora of the region as sketched by Guppy,* and also with the distribution of the Lepidoptera independently remarked by Woodford.*It is thus opposed to the theory of a migration westward from America across a Mesozoic Pacific continent as advocated by Hutton.*
* Guppy—Trans. Vic. Inst., 1896. (Reprinted on p. 20 of the "General Account.")
* Woodford—Geogr. Journ., vi., 1895, pp. 349-350; also ante, p. 90.
* Hutton—Proc. Linn. Soc. N.S.W., xxi., 1896, pp. 36-47.