Sessional_Paper_1907 — Page 824

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those of the rattus, the curve being almost at right angles to the inferior maxilla, and the wearing face of the tooth is almost parallel to the wearing surface of the molars. This rat is larger and its whole build more robust than that of the black rat, and the general con- formation more fitted for burrowing than climbing.

The common mouse: Mus musculus.

This animal is too well known to reed description although the Chinese do not appear to recognise it as a species distinct from the rat. It resembles rattus more than decumanus.

The musk rat: Sorex giganteus.

As already stated this is not a rat proper or even a rodent. It belongs to a rather moblike group, the insectivorae, which includes such widely differing animals as the mole, hedgehog, and shrew. This animal is caught in traps much less frequently than the others. Its outline closely resembles a rat but it is appreciably smaller than the rattus. Its first characteristic is its overpowering musky odour which appears to have given it the Chinese name (d) So Shu, the "stinking rat.'

It is purely nocturnal in its habits, has a peculiar bat-like cry and frequents sewers, drains, and garbage heaps where it feeds on decaying animal matter. It sometimes finds its way into dwelling houses and its odour gives notice of its arrival. It seems to be regarded with particular aversion by Chinese who try to get rid of it by killing or driving it away. It is said to be looked upon by some as a very noxious animal, its breath even being reput ed to be fatal to man or animals, and certain it is that no cat will touch it and only a very few dogs will attempt to kill it. On the other hand we have been told that its presence in a house is indicative of coming good luck in money matters and that Chinese like to see it there. It is covered with a soft, fine, almost black fur. Under this on each flank there is a band of stiff closely set bristles, from between which exudes an odorous fluid, the product of a particular gland. The two middle superior incisors are hooked, and dentated at the base; the lower ones are slanting and elongated. Five small teeth follow on each side of the former and only two follow the latter. There are besides on each jaw three bristled molars, and finally on the upper one a small tuberculated tooth. The snout is greatly elongated and semiprehensile. The nostrils open on the side and are fitted with a valve arrangement which enables the auimal to forage under water. The eyes are rudimentary. It is an excellent swimmer and diver. Its gait is peculiar, owing to its short legs it moves along as if on wheels,

Undetermined rats.

Under this heading we have included such rats as show in the one animal characters usually considered typical of rattus and decumanus, eg., the short thick tail of Mus decu- manus with the long ears of Mus rattus.

Young rats.

These include baby rats of both species as the young are so much alike that differentia- tion is impracticable.

Specimens.

We have prepared specimens of the skulls of these rats and mounted them for future reference.

Comparative frequency.

Taking the undecomposed rats which have arrived at the Public Mortuary during the last two months as indicative of the comparative numbers found of each species in Hongkong we find roughly the following percentages,

Black rats: Mus rattus,......

Brown rats: Mus decumanus,

Mice: Mus musculus,

Musk rats: Sorex giganteus,

Undetermined rats, size of Mus rattus, Baby rats, undetermined,

12 % ..18 %

48 %

2

+

5 % .15 %