MARSUPIALIA. 



263 



The canines (c.fig. 86 and 87,) are constant 

 in regard to their presence, but variable in size ; 

 they are always very small in the lower jaw. 



With respect to the functional premolars 



, these are always in contact with the 



molars, and their crowns reach to the same 

 grinding level ; sometimes a second premolar 

 is similarly developed in the upper jaw, 

 as in the Phal. Cookii, and as in the great 

 flying Phal angers, (Petaurus Tuguanoides, 

 fig. 88) but it is commonly absent, or re- 

 placed by a very minute tooth, shaped like a 

 canine ; so that in the upper jaw, between the 

 posterior or functional premolar and the in- 

 cisors, we may find three teeth, of which the 

 posterior is the largest, as in P/iul. Cookii, or 

 the smallest as in Phal. cavifrons ; or there 

 may be only two teeth as in Phal. ursina and 

 Phal. vulpina, and the species, whatever that 

 may be, which M. Fr. Cuvier has selected as 

 the type of the dentition of the Genus. 



In the lower jaw similar varieties occur in 

 these small and unimportant teeth ; e. g. there 

 may be between the procumbent incisors and 

 the posterior premolar, either three teeth as in 

 Phal. Cookii and Phal. cavifrons, or two, as 

 in Phal. ursina, Phal. maculata, Phal. chry- 

 sorrhoos ; or finally one, as in Phal. vulpina 

 and Phal. fuliginosa. The most important 

 modification is presented by the little Plial. 

 gliriformis of Bell, which has only three true 

 molars on each side of each jaw. As these 

 modifications of the teeth are unaccompanied 

 by any change of general structure or of habit, 

 whilst those teeth which most influence the diet 

 are constant, it is obvious that these differences 

 of dentition are unimportant, and afford no 

 just grounds for subgeneric distinctions. 



The Phalangers, being provided with hinder 

 hands and prehensile tails, are strictly arboreal 

 animals, and have a close external resemblance 

 to the Opossums, by which name they are 

 generally known in Australia and the Islands 

 of the Indian Archipelago, where alone they 

 have hitherto been found. They differ from 

 the Opossums chiefly in their dentition; and in 

 accordance with this difference their diet is 

 more decidedly of a vegetable kind.* The 

 Australian Phalangers feed chiefly on the ten- 

 der buds and the leaves of Eucalypti : but 

 according to Temminck,f the Indian Phalan- 

 gers are omnivorous, and combine insects with 

 fruits and leaves. Mr. OgilbyJ states that 

 both " the Phalangers and Petaurists display 

 so decided a preference for live birds, as to 

 make it probable th it these constitute a main 

 portion of their food in a state of nature." I 

 find, however, that the intestinal canal, and 

 especially the ccecnm, offers so great an addi- 

 tional development in length, as, with the cor- 

 responding predominance of the incisors, and 

 atrophy of the canines, to indicate clearly a 



* In the stomach and intestines of specimens 

 sent to me in spirits from Australia, I have never 

 found any other alimentary substances but those of 

 a vegetable nature. 



f Monographies de Mammalogie, p. 3. 



J Mug. Hist. Nat. 1837, p. 458. 



natural and constant tendency in the Phalangers 

 to a vegetable diet. Guided therefore by the 

 totality of their organization, I am led to place 

 them in a distinct section from that which con- 

 tains the Opossums, but, in that section, they 

 come the nearest to the true Opossums. The 

 Phalangers of the Indian Isles have short ears 

 and the greater part of the tail naked. To this 

 group have been applied the names Ceonyx, 

 Caucus, and Balantia ; the Australasian Pha- 

 langers have moderately long ears, and the 

 greater part, or else the whole of the tail is 

 covered with hair. All the species possess 

 considerable freedom of lateral movement in 

 the anterior digits, and in some small species, 

 as Phal. gliriformis, Bell, they appear to be 

 naturally divided into two groups, the two 

 outer being opposed to the three inner fingers. 

 To the hairy-tailed Phalangers exhibiting this 

 character, Mr. Ogilby gives the subgeneric 

 name Pseudochcirus, restricting the term Phalun- 

 gista to the remaining species. With reference 

 to the subgenera Cuacus, Bulantia, Pseudo- 

 cheirus, &.c. I heartily concur in the opinion 

 of the experienced and judicious Temminck,* 

 that these numerous sections are perfectly use- 

 less, and a burthensome charge to the memory. 

 Genus PETAURUS. 



There are many species of Marstipialia limi- 

 ted to Australia and closely resembling, or 

 identical with, the true Phalangers in their den- 

 tal characters and the structure of the feet. I 

 allude to the Petaurists or Flying Opossums : 

 these, however, present an external character 

 so easily recognizable, and influencing so ma- 

 terially the locomotive faculties, as to claim 

 for it more consideration than the modifica- 

 tions of the digits or spurious molars which 

 we have just been considering in the Pha- 

 langers. A fold of the skin is extended on 

 each side of the body between the fore and 

 hind legs, which, when outstretched, forms a 

 lateral wing or parachute ; but which, when the 

 legs are in the position for ordinary support or 

 progression, is drawn close to the side of the 

 animal by the elasticity of the subcutaneous 

 cellular membrane, and there forms a mere te- 

 gnmentary ridge. These delicate and beautiful 

 Marsupials have been separated generically from 

 the Phalangers under the name of Petaurus: 

 they further differ from the Phalangers in want- 

 ing the prehensile character of the tail, which, 

 in some species of Petaurus, has a general 

 clothing of long and soft hairs, whilst in others 

 the hairs are arranged in two lateral series. 



Now in the Petaurists there is as little con- 

 stancy in the exact formula of the dentition as 

 among the Phalangers. The largest sj.ecies of 

 Petaurus (Pet. Taguanoides) for example, is 

 almost identical in this respect with the Pha- 

 langiata Cookii, which M. Fr. Cuvier has 

 therefore classed with the Petauri. Those 

 teeth of Pet. Taguanoides which are sufficiently 

 developed, and so equal in length, as to exer- 

 cise the function of grinders, or in other words, 

 the functional series of molars, includes six 

 teeth on each side of the upper jaw, and five 



* Loc. cit. p. 10. 



