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). 



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 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 paits of the eastern continent produce several species. 



G. indicus; Dipus indicus, Hardw., Linn. Trans. VIII, pi. vii; 

 Herine, Fred. Cuv, Mammif. (The India Gerbil). Size of the fat 

 Dormouse; fawn coloured above, whilisli beneath; tail longer than 



* Hypudtsus variegatus, Lichtenst. var. flava. — Meriones syenenses, Id. ; to wliich 

 must be added the Arvicola messor, Le Comte, Arv. hortensis, Harl., or Sygmodov, 

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



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

 the Hypudaus obesus, Lichtenst., the Mus ruficaudltus, 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 floridaiius 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 \\ithout. 



^^ (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 Surmiilot, M. deciimanus. Very lately, however, the 

 M. ratlus 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, M. giganteus, and was sent from Bombay by that great patron of sci- 

 ence, the Earl of Clare. Here, also, are to be seen some Barbarymice, the M. bar- 

 barus of Linnasus; since whose time the species entirely eluded all observation, imtil 

 it was recently recovered by the Zoological Society. It is a species coiumon in Bar- 

 bary. The Long-tailed Field-Mouse, M. 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 upon 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," 

 varj' 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 diflRculty found. — 

 Eng. Ed. 



