MAMMALS THAT GNAW. 101 



The beautiful little large-eyed marines, known as gerbils, typify a third 

 sub-family, characterised by the narrowness of the incisors, the sub-division 

 i>t the crowns of the molars into transverse laminee, the 

 generally large size of the auditory bulla of the skull, and The Gerbil 

 the elongation of the hind-limbs. From the other genera, Group 



the gerbils (Gerbillus), which range over Southern Europe, (Gerbillince). 

 Asia, and Africa, are distinguished by the deeply grooved 

 upper incisors, and the circumstance that the first molar has one, the second 

 two, and the third three transverse laminae ; the long tail being tufted at the 

 tip Gerbils are inhabitants of desert districts, where they burrow in tho 

 sandy soil. Some writers separate certain species as Merioncs. The short 

 and club-like form of the fleshy tail, as well as the very large size of tho 

 auditory bulla of the skull, serve to distinguish the African genus Pachy- 

 uromys, in which the narrow incisors are faintly grooved. Three other small 

 genera from Africa, namely, Mystromys, Otomys, and Dasymys, differ from 

 the gerbils and from one another in the structure of the molars ; they are all 

 typically South African, but the second has also been recorded from East 

 Africa and the Congo. A fifth genus (Malacomys), represented by a single 

 species from the Gabun, connects the gerbils with the rats, having the teeth 

 and limbs of the former, but the long scaly tail of the latter. 



Two genera of very large long-haired rats from the Philippine islands 

 represent a sub-family in which the incisors are very broad, the molars divided 

 into transverse laminre, and the claws large. In Phlceomys, 

 of which there is but a single well-defined species, the ears The Philippine 

 are small and hairy, the tail moderate and sparsely haired, Rats (Phlceo- 

 and the auditory bulla very small ; the first molar having myince). 

 three, and the others two laminae. The second genus 

 (Crateromys) includes one very large greyish species from Luzon, which may bo 

 compared in size to a small marmot, and has a totally different type of molars. 



This group, which is confined to Africa south of the Sahara, is typified by 

 the two species of Dendromys, and is characterised by the convexity of the 

 incisors, the rooted and tuberculated molars, hairy ears, and 

 long claws. The members of the typical genus have tho The Tree-Mice 

 habits of dormice & slender build, grooved incisors, and a (Dtndromyince.) 

 long, scaly, thinly-haired tail. Steatomys also has grooved 

 incisors, but of stouter form, and a rather short, thickly-haired tail ; while 

 Lophuromys differs by its smooth incisors, and the fine flattened bristles 

 which replace the hair. ^The fourth genus is Limacomys. 



The large, generalised, and almost cosmopolitan group of the cricetine 

 Muridcs is characterised by the rooted upper molars carrying two longitudinal 

 rows of tubercles. It is typified by the hamsters (Cricetus) 

 of the Old World, which are confined to Europe and Asia, Cricetine Group 

 arid are characterised by having six tubercles on the first (Cricetince}. ' 

 upper molar, large cheek pouches, and a very short tail. 

 The true hamster (C. frumentarius) is a burrowing species, well known on the 

 Continent from the large amount of food it accumulates in its subterranean 

 dwelling. The white-footed mice (Sitomys) of the New World form a very 

 large, closely allied group, in which cheek pouches may be present or absent. 

 They are divided into a number of sub-genera, according to habits, bodily 

 form, dentition, etc., which have been named Rhipidomys, Oryzomys, Calomys, 

 Vesperimus, Onychomys, Scapteromys, Phyllotis, Acodon, and Oxymycterus. 

 S. hydrobates is peculiar oil account of its fringed feet and aquatic habits j 



