154 SIXTH REPORT — 1836. 



narrative of Captain Back's journey. The latter animal agrees 

 exactly withEschscholtz's in the remarkable post-auricular black 

 bar, in the general colour, and in the relative length of the fur 

 on the different parts of the body, but differs in some minor 

 points, and particularly in its smaller size, which may, how- 

 ever, be owing to its youth. 



The only species of the restricted genus miis which is un- 

 equivocally indigenous to North America * is the miis leucopus 

 of Rafinesque ; and this so closely resembles mus sylvaticus of 

 Europe that there ai*e scarcely grounds for impugning the 

 opinion of the older naturalists, who considered it to be the 

 same species. In my dissections I did not succeed in detecting 

 cheek-pouches, but Dr. Gapper has discovered cheek-pouches 

 in a Canadian animal differing in no respect from it in exterior 

 appearance, which he has therefore named cricetus mi/oides, 

 and figured in the Zoological Journal. The mus leucopus is 

 found everywhere, from the arctic circle down to the United 

 States, and some authors state that it is common throughout 

 the Union ; but Dr. Harris says that it is not found in Massa- 

 chusetts. It readily domesticates itself in the habitations of 

 man, wherever the mus decumanus, rattus, and musculus, in- 

 troduced from the other side of the Atlantic, have not pene- 

 trated. The myoxus virginicus of Reich, quoted in Fischer's 

 synopsis, seems very closely allied to mus leucopus ; it is an 

 inhabitant of the foot of the Alleghanies. The mus nigricans of 

 Rafinesque is supposed to be merely the common black rat 

 {;rattus). 



The merio7ies lahradorius inhabits America from the 60th 

 parallel to an unascertained distance southwards. We have 

 received several examples from different parts of the United 

 States, and the canadensis of authors has not been proved to be 

 a distinct species. Rafinesque indicates others, viz., soricinns, 

 leonurus, hudsonius, megalops, and sylvaticus ; but his notices 

 ai'e not sufficiently detailed for scientific purposes. Dr. Mit- 

 chell is equally vague in his account of a meriones sylvaticus. 



Neotoma Drummondii abounds in the Rocky Mountains and 

 Jloridana in Florida. As these animals resemble the myoxi in 

 external form, it is desirable to know whether, like them, they 

 are destitute of a cjecum. They build well-protected nests 

 above ground, instead of burrowing like the meadow-mice, and 

 appear to be omnivorous, like the common rat, than which 

 they are even more destructive. Of M. Le Comte's neotoma 



* A species inhabits Port Famine, in the Straits of Magellan, mus magella- 

 nicus. (King, Zool. Proc, 1835.) 



