306 MvniDM. 



species were sent home by Mr. Fraser from Ecuador, 

 which had the end of the tail and all the feet white. It 

 will be evident, therefore, that the markings of white 

 must be regarded as accidental, and not as indicative of 

 specific difierences. 



The larger species of this genus, which are usually 

 denominated Rats, differ in some trifling particulars from 

 the Mice, and have by some naturalists been considered 

 as constituting a distinct genus, of which opinion is our 

 friend Mr. Hogg, who proposes for the former the generic 

 term Rattus : there does not, however, appear to be a 

 sufficient ground for such a separation. The present 

 species is smaller than the Brown Rat ; the head is 

 more elongated ; the muzzle taper and divided, and 

 garnished with numerous long black hairs ; the upper 

 jaw projects far beyond the lower, which is remarkably 

 short ; the tongue is smooth ; the nostrils open and 

 crescent-shaped ; the ears rounded, simple, naked, half 

 as long as the head ; the eyes large, not particularly 

 prominent. The feet are decidedly plantigrade, with 

 five toes on each ; but the thumb on the anterior pair 

 is concealed within the skin, excepting the terminal 

 joint, with its claw. The soles of all the feet are tuber- 

 culated. The tail longer than the body, almost without 

 hair, and covered with numerous rings of scales. Colour 

 of the upper parts greyish-black, sometimes brownish- 

 black, and we have seen a few specimens in which the 

 back has been of a dark brownish-grey, and their resem- 

 blance to the Mus alexandrinus* has been very remark- 



* An interesting paper was published by M. A. de I'lsle in the " Annales 

 des Sciences Naturelles " for 1866, detailing the results of a long series of 

 experiments on the inter-breeding of M. rattus with the M. alexandrinus 

 of Southern Europe. M. de I'Isle arrived at the conclusion that these two 

 forms must be regarded merely as geographical races of one species, and con- 

 sidered M. alexandi-inus to be the oldest, or parent breed. 



