114 MAMMALS OF THE PACIFIC WORLD 



about seven and one-half to eight and one-fourth inches in total 

 length, of which slightly more than half is tail. 



Two small mice are about the same size as the house mouse 

 and are not very unlike it. 



The Wood Mouse (Apodemus) of Formosa, Japan, and the 

 Kuriles, is a Eurasian type found from the British Isles to east- 

 ern Asia. The tail is long and nearly naked. Wood mice are 

 yellowish brown above, white below, and have white feet. 



The Pygmy Tree Rat {Hceromys), found in North Borneo 

 and Celebes, has the tail longer than the house mouse, and the 

 first toes on front and hind feet are thumb-like and opposable. 



The Common Rats (Rattus) are world-wide in distribution. 

 Three kinds of rats have been carried involuntarily by man dur- 

 ing the last three hundred years to the ports of the Pacific, 

 whence they have spread widely. The Norway or brown rat 

 (Rattus norvegicus), which is the common house rat through- 

 out the northern United States and Europe, is the largest of 

 the three, measuring fifteen or sixteen inches long with the tail 

 a little less than half of this ; the females are smaller. The 

 brownish gray fur is coarse, and the ears small. The scales of 

 the tail number about twenty-five to the inch. In the tropics 

 this rat is usually confined to seaports. The black rat and Alex- 

 andrine or roof rat, color varieties of a single species (Rattus 

 rattus), are even more widespread in the warmer countries. 

 They are relatively large animals, sixteen or seventeen inches 

 long, with the tail a little more than half this length. The tail 

 scales are finer than in the Norway rat, and the ears are large, 

 reaching to the middle of the eye when laid forward. The black 

 rat is recognized by its color, but the roof rat is colored much 

 like the Norway rat and many native ones. Wild races of Rattus 

 rattus are known in the islands between the Malay Peninsula 

 and Celebes ; east of this they are replaced by other species. 



The small rats commonly living in native houses on the islands 

 are all members of the Rattus concolor group, which occur from 

 the mainland of Asia to Hawaii and the Marquesas Islands. The 



