126 MAMMALIA. 
Warm climates produce rats similar in every particular to those of 
which we have just spoken, except that their tails are more hairy* (a). 
Gersitius, Desm.—MeEriones, /llig. 
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 are some- 
what longer in proportion than those of rats in general, and their thumb 
and little toe slightly separated. Their tail is long and hairy. The 
sandy and warm parts of the eastern continent produce several species. 
G. indicus; Dipus indicus, Hardw., Linn. Trans. VIII, pl. vii; 
Herine, Fred. Cuv. Mammif. (The India Gerbil). Size of the fat 
Dormouse; fawn coloured above, whitish beneath; tail longer than 
* Hypudeus variegatus, Lichtenst. var. flava.—Meriones syenenses, Id.; to which 
must be added the Arvicola messor, Le Comte, Arv. hortensis, Harl., or Syemodon, 
Say; distinguished, however, by hairy ears, like the Otomys. 
Another group, with hairy tails also, but whose teeth wear away faster, will include 
the Hypudeus obesus, Lichtenst., the Mus ruficauditus, Id. His Meriones sericeus 
should form a third, characterized by the projecting ridges of the molars, which al- 
ternately catch in each other. 
We then have to group the Neotoma floridanum of Say, or the Arvicola floridanus of 
Harlan, and the Arvicola gossypina of Le Comte, two rats which, size excepted, are 
very similar even in their colours, whose teeth, provided with roots, if worn a little, 
have 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. 
kes (a) Amongst the specimens of this genus in the Zoological Gardens in Lon- 
don, are the Mus Rattus, a species so long known in this country as to be considered 
aboriginal to it. This rat was formerly very abundant, but for many years has been 
almost wholly displaced by the Surmulot, M. decumanus. Very lately, however, the 
M. ratius has very unaccountably re-appeared in several places in London. A spe- 
cies not described by Cuvier is to be seen in the gardens in Regent’s Park; it is the 
Gigantic Rat, MM. giganteus, and was sent from Bombay by that great patron of sci- 
ence, the Earl of Clare. Here, also, are to be seen some Barbary mice, the M. bar- 
barus of Linneus; since whose time the species entirely eluded all observation, until 
it was recently recovered by the Zoological Society. Itis a species common in Bar- 
bary. The Long-tailed Field- Mouse, A. sylvaticus, will also be found in the above 
collection. The singular nest of the Harvest-Mouse, M. messorius, has been ren- 
dered too interesting an object of contemplation, by White of Selborne, to be passed 
over. He found it suspended upen the head of a thistle, in a wheat-field. The nest 
was of the size of a cricket-ball, was perfectly round, and was composed of blades of 
wheat, which were platted together with wonderful art. What was most curious was 
the absence of any aperture in the ball, for exit or entrance; and yet, the particular 
nest which Mr, White examined contained eight young, which so completely occu- 
pied the cavity, that it was apparently impossible for the creatures to turn themselves, 
in order to seize the mother’s teat; and still more was it difficult for the mother to 
find room in the nest. These nests, observes the author of the “ British Naturalist,” 
vary in shape, being round, oval, or pear-shaped, with a long neck, and are to be 
distinguished from those of any other mouse, by being generally suspended on some 
growing vegetable—a thistle, a bean-stalk, or some adjoining stems of wheat, with 
which it rocks and waves in the wind; but, to prevent the young from being dis- 
lodged by any violent agitation of the plant, the parent closes up the entrance so 
uniformly with the whole fabric, that the real opening is with difficulty found.— 
Ene. Ep. 
