Several other forms of Muridæ, with rooted molars, have been distinguished, and all are inhabitants of the Eastern hemisphere. The genera _Phlœomys_ and _Nesokia_, each including a single species, form the group PHLÆOMYINÆ, characterised by having broad incisors and the molars divided by transverse plates of enamel. The characters of the skull are as in the Murinæ. _Phlœomys Cumingii_ is from the Philippine Islands; _Nesokia Griffithii_ inhabits Northern India. _Platacanthomys lasiurus_, the only known species of the group PLATACANTHOMYINÆ, resembles a Dormouse in its form, and is nearly allied to the preceding species, but has the fur of its back mixed with long, flattened, bristle-like spines. It is a native of the Malabar coast. [Illustration: SKULL OF THE WATER-MOUSE.] The WATER MICE (_Hydromyinæ_) are of particular interest, as being a small group, exclusively confined to the Australian region, and presenting the exceptional character among the Rodents of having only two molars on each side in each jaw. These teeth, are rooted, and divided into transverse lobes by ovate enamel lobes; the front tooth is much larger than its fellow. The _Hydromys_ are small rat-like animals of slender form, with long tails, rather densely clothed with short hairs, and short limbs. The hind feet have much stronger claws than the fore feet, and their toes are partially webbed. Five species of this group are known from Australia and Van Diemen’s Land, where they inhabit the banks of the streams. The best known are the Yellow-bellied and the White-bellied Water Mice (_Hydromys chrysogaster_ and _leucogaster_), both of which inhabit New South Wales, and the latter is also found in Van Diemen’s Land. The Sooty Water Mouse (_H. fuliginosus_) is an inhabitant of Western Australia. In the SMINTHINÆ--a group which includes only the genus _Sminthus_, founded for the reception of a rat-like Rodent (_S. vagus_) first discovered in the Crimea, but now known to range from Hungary, Finland, and Sweden, through Russia to the banks of the Irtisch and Yenisei, and into Tartary (Bokhara)--we find another exceptional character of the molar teeth. There are four of these teeth on each side both above and below, the first and fourth of which are much smaller than the intervening ones. In this animal the ears are rather long and pointed, the legs are rather short, and the tail is about as long as the body, and clothed with short hairs. [Illustration: TEETH OF SMINTHUS.] In the remainder of the Muridæ, the molars, which are again only three in number on each side, are generally rootless, although occasionally the growth of the teeth stops and they close up below. The molars are composed of triangular prisms placed alternately. Two groups are thus characterised, namely, the Voles and the Zokors.