RODENTIA. 113 



The Black Rat (M. rattus, Lin.), which tlie ancients have not alhided to, and wliich appears to have entered 

 Europe during the middle ages. It is more than double the size of the Mouse in all its dimensions. The fur is 

 liiackish [with the ears much larger, and the tail longer, than in the foUomng. There is a brown variety of this 

 species, which is common in Paris, and appears to have been figured by M. F. Cuvier as the Sumiidot.] 



The Brown Rat, or Surniulot (M. decumanus, Lin.), which did not pass into Europe till the eighteenth century 

 and is now more common in large cities [and elsewhere, except in remote isolated localities,] than the Black Rat 

 itself; it is a fourth larger than that species, and is also distinguished by its brown colour. This animal appears to 

 belong to Persia, where it lives in burrows : it was not till 1727, that, after an earthquake, it arrived at Astracan 

 by swimming across the Volga. 



It would seem that the Black Rat, also, originated in the East ; and these two large species, together with tbe 

 Mouse, have been transported in ships to all parts of the globe. 



[Of the very numerous others, it must suffice to name the huge Bandicoot Rat of India (M. giganteus, 

 Hardw.), which is much larger than the Surmulot. Those indigenous to South America have more complicated 

 folds of enamel to their molars.*] Some have spines mingled with their fur, as 



The Cairo Mouse (M. cahirinus, Geoff.), which has spines on the back in place of hairs, and was noticed by 

 Aristotle. 



[Only two strictly indigenous British Mice have hitherto been described : the first, extremely diminutive, is the 

 Harvest Mouse (M. messorius, Shaw), with short ears, and red fur similar to that of the Common Dormouse : it 

 constructs a beautiful round or pear-shaped nest, attached to corn-stems, or placed in low bushes ; and is remark- 

 able for its tail being slightly prehensile at the extremity. Tlie second is commonly termed the Long-tailed Field 

 Mouse (M. sylvatictis), and might almost form a separate subgenus ; it rather exceeds the common Mouse 

 in size, with proportionately larger ears, and much larger and very brilliant eyes; a brown mark in the centre 

 of the chest : it is a pretty and very active species, more generally diffused than the Harvest Mouse, and never 

 enters buildings, where the other is often carried with the sheaves.] 



Wai-m climates produce Rats, similar in every detail to those of \\hicli we have just spoken, except 

 tliat their tails are more hairy. Such are 



Hi/pudaus variegatus, Licht., var. flava; Meviones syenensh, Id. To which must be added the Arvirola 

 messor, Le Conte ; Arv. hortensis, Harl., or Sygmodon, Say, distinguished however by its hairy ears, like 

 the Otomys. 



Another group, also with a hairy tail, but the teeth of which wear away faster, comprises the Ilypudceus nbestis, 

 Licht., the Mtcs riijicniidiis, Id., and also the Mcriones sericeiis of the same naturalist, characterized by the 

 projecting ridges of the molars, which alternately catch in each other. 



We have then to group the Neoioma Jloridanum of Say, or the Arvicola floridana of Harlan, and the An-icola 

 gossypina, Le Conte, two species whicli, size excepted, are very similar even in their colours, and the molars of 

 which, provided with roots [after a while], when worn a little, have crowns similar to those of the Arvicola-. [The 

 tail in one of them is covered with hair of tolerable length. Both inhabit North Ameiica. 



Reithrodon, Waterh., requires also to be introduced here, distinguished by its grooved upper incisors, its arched 

 and Rabbit-like head, great eyes, and large and round ears. Three or four species are known, from South 

 America, where they w'ere discovered by Mr. Darwin. 



The Pseudomys of Gray is another Rat-like animal, remarkable for inhabiting New Holland : the anterior molar 

 of its lower jaw is however more compressed and elongated, and there is a claw on its rudimentary thumb. The 

 species, Ps. ausfralts, inhabits holes in swampy places, at Liverpool plains. 



It is necessary also to introduce here the Hapalotis albipes, Licht. ; Cnnilitrus con.it rictus, Ogilby ; another 

 rodent from New Holland, the size of a Rat, with delicate ample ears, and a long, hairy, and somewhat tufted tail. 

 It is remarkable for constructing an above-ground habitation, so fii-mly interlaced with thorny twigs externally, 

 as to repel the Dingo or semi-wild Dog of that country.] 



The Gerbils {Gerbillus, Dcsm. ; Meriones, Illig.) — 

 Have molars scarcely rlifFering from those of the Rats, merely becoming sooner worn, so as to form 

 transverse ridges. Their upper incisors are furrowed with a groove ; their hind feet are somewhat 

 hmger in proportion than those of Rats in general, with the thumb and little toe but slightly sepa- 

 rated : their tail is [very] long and hairy, [and generally tufted]. 



The sandy and warm parts of the eastern continent produce several species, [mostly of a light bull' colour, white 

 underneath]. 



TnK Merions (Mfirimies, F. Cuv.), — 



Which we separate from the Gerbils, have the hind feet still longer, the tail nearly naked, and a ver} 

 small tooth before the superior molars ; characters which approximate them to the Jerboas : theii- 

 superior incisors are grooved, as in the Gerbils, and their toes also are similar. 

 There is a small species in North America, Mus canadensis, Pen.; Dipus canadensis, Shaw; D. americaniit, 



<■ Certain of these, the upper lip of which is Rearcely fissured, com- | -South Africn, which constitute t\ic Drnilriimys of Smith : tiiey scitrcclr 

 pose the H'</<ii/ii/«», Uraciilt, Tiiere arc ulso some arborenl Mice in i (lifTor in structure from llic liritisli Harvest Mouse— Ko. 



