144 MAMMALIA. 



Fewer species have been observed of the size of the Mouse. 

 M. cahirinus, Geoff., Descr. de I'Eg. Mammif. (The Cairo 

 Mouse.) Spines on the back in place of hairs noticed by 

 Aristotle. 



One species only is known in France that does not reside in 

 houses, the M. sylvaticus. (Field Mouse.) Buff. VII, xU, 

 which is hardly larger than the Mouse, and is distinguished 

 from it by its red fur. It does much injury to trees, and some- 

 times penetrates into gardens. 



It seems, however, that in some of the provinces there is a 

 smaller and grey species, which has also been observed in Eng- 

 land, {M. mcssorius, Shaw, Vol. II, Pari 1, Frontisp.) and a 

 third still more diminutive (A/, pumilus, Fr. Cuv. Mammif.).{l) 

 Warm climates produce Rats, similar in every particular to those 

 of which we have just spoken, except that their tails are more 

 hairy. (2) 



Gerbillus, Desm. Meriones, Illig. 



The Gerbils have molars that differ very little from those of Rats, 

 merely becoming sooner worn, so as to form transverse elevations. 

 Their superior incisors are furrowed with a groove ; their hind feet 



(1) To this division, most probably, belong the M. agrarius, M. minutus, M. so- 

 ricinus, M. vagus, M. betulinus, M. striatus, M. barbarus, Schreb. 



Here also should come the enormous Mus giganteus, Hardw. Linn. Trans. Vll, 

 xxviii. 



There should be likewise added tlie Mpumilio, Sparm. the M. cyanus, Molina, 

 and several other species, some of which are not even mentioned by authors, and 

 others which are described with too little comparison. This is the reason why most 

 of the Rats of Azzara cannot be properly classed until they are re-examined. The 

 same observation applies to a great many of the Rodentia of M. Rafinesque. Their 

 desci'iptions are too short to be of any use. 



(2) Hypudxus variegatus, Lichtenst. var. flava. Bleriones syenensis. Id. to which 

 must be added the Jlrvicolu rnessor, Le Conte, ^rv. horiensis, Harl. or Sygniodon, 

 Say, distinguished however by hairy ears, like the Otomys. 



Another group, with hairy tails also, but whose teeth wear away faster, will in- 

 clude the HypudsEUs obesus, Lichtenst. the Mus ruficaudatus. Id. His Meriones se- 

 riceus should form a tliird, characterized by the projecting ridges of the molars, 

 which alternately catch in each other. 



We then have to group the Neotoma fioridanum of Say, or the Arvicola Jlorida- 

 nus of Harlan, and the Jlrvicola gassy pina, Le Conte, two Rats which, size excepted, 

 are very similar even in their colours, whose teeth, provided with roots, if worn a 

 little, liave crowns formed like those of the Arvicola. 



These animals, however, previous to a definite classification, require to be com- 

 pletely examined and compared, internally as well as without. [Sec Append. IX 

 of Am. Ed.] 



