110 



MAMMALIA. 



In the Indian Archipelago there is one nearly the size of a Cat (Sc. petaurista, Lin.) : but the same Archipelago 

 produces smaller ones, as the Sc. sagitta, distinguished from the rest, the small ones especially, by its membrane, 

 which, as in Pt. petaurista, forms an acute projecting angle behind the tarsus. 



[M. F. Cuvier has subdivided this group into the Taguans (Pteromys), and Assapans (Sciuropterus), which 

 latter term he applies to the smaller species, the hairs on the tail of which are arranged distachously : there are 

 several eastern species, however, which appear to connect the two together.] 



The Aye-Aye (Cheiromys, Cuv.), — 

 The inferior incisors of which are still more compressed, and above all, more extended from front to 

 back, resembling plough-shares. Their feet have each five toes, of which four of the anterior are 

 excessively elongated ; the medius being much more slender than the others ; in the hind-feet, the 

 thumb is opposable to the other digits ; so that in this respect these animals are to the other rodents, 

 what the Opossums are among the Carnaria.* The structure of their head is otherwise very different 

 from that of the other Rodentia, presenting a closer relationship with the Quadrumana [among which 

 this remarkable genus is now ranged by almost general consent. It is, in fact, in the aggregate of its 

 conformation, a Lemurine animal : in which group we have already seen that the lower canines axe 

 singularly modified, projecting forwards, and being approximated to each other ; insomuch that the 

 intervening incisors (except in Galceopithecus) are consequently extremely compressed and narrow, 

 one pair of them being even sacrificed in the Indris. In the present genus, the whole of the incisors 

 disappear, as in the ordinary Rodentia ; the canines of both jaws occupying their site : but it is very 

 doubtful whether, as in the true Rodents, these teeth have persistent formative pulps, as there does 

 not exist another known instance of continuously growing teeth in any animal pertaining to the great 

 divisions of Primaria and Carnaria.f What little is known of the osteology of Cheiromys is strictly 



Lemurine ; and no rodent possesses the rotation of the bones of the 

 fore-arm, and free separate movement of the limbs as prehensile in- 

 struments, which are observed in this genus. Its habitat even is 

 Madagascar, the metropolis of the Lemurine group of animals.] 



One species only is known, discovered by Sonnerat (Sciurus madagascar- 

 iensis, Gm.) ; as large as a Hare, of a brown colour, tinged with yellow ; tail 

 long and thick, with some black bristles ; and large naked ears. It is a 

 nocturnal animal, the movements 01 which seem painful to it ; lives in 

 burrows, and employs its long slender digit to convey food to its mouth. 



Linnaeus and Pallas have brought together in one single group, 

 under the general name of 



Rats (Mus, Lin.), — 



All the rodents possessed of clavicles which they could not distin- 

 guish by some obvious external character, such as the tail of the 

 Squirrels or that of the Beaver ; from which resulted the utter impos- 

 sibility of assigning to them any common character : the greater 

 number had merely pointed lower incisors, but even this character 

 was subject to exceptions. 



Gmelin has already separated the Marmots, Dormice, and Jerboas ; 

 but we carry their subdivision much further, from considerations founded on the form of their 



grinders. 



The Marmots (Arctomys, Gm.) — 



Have, it is true, the inferior incisors pointed, as in the greater number of animals comprised in the 

 great genus of Rats ; but, as in the Squirrels [to which superior group they indubitably appertain], 

 they have five molars on each side above, and four below, all of them sharply tuberculated ; accord- 

 ingly, some of the species are inclined to eat flesh, and feed upon insects as well as vegetables. They 

 have four toes, and a tubercle in place of a thumb, to their fore-feet ; and five toes to their hind feet. 

 In other respects, these animals are nearly the direct reverse of the Squirrels ; being heavy, with short 

 limbs, a hairy tail of middle length or short, a large flat head, and they pass the winter in a state of 



k 



Fig 45.— The Aye Bye. 



* The Opossums were arranged among the Carnaria in the author's ' t The Wombat presents the only instance amongst the Mar- 

 first cilitiou.— Ko. . supiata. 



