MARSUPIALIA. 



261 



the preceding Bandicoots the canines are long 

 and well developed, but the true molars have 

 the grinding surface worn down flat in the full- 

 grown specimens which I have had the oppor- 

 tunity of examining. 



The marsupial pouch in the Bandicoots, at 

 least in the full-grown females of Per. nasuta, 

 Per. obesula, and Per. Lagotis, has its orifice 

 directed downwards or towards the cloaca, con- 

 trariwise to its ordinary disposition in the 

 Marsupials : this direction of the pouch evi- 

 dently relates to the procumbent position of 

 the trunk when supported on the short fore 

 and long hind legs. In the stomach and in- 

 testines of a Perameles obesula I found only 

 the remains of insects ; and in the examination 

 of the alimentary canal of a Per. nasuta, Dr. 

 Grant obtained the same results. Nevertheless 

 the Perameles Lagotis, lately living at the Zoo- 

 logical Gardens, refused meat and meal-worms, 

 and subsisted on vegetable food exclusively. 

 Genus CHCEROPUS. 



The singular animal on which Mr. Ogilby 

 has founded this genus, is briefly noticed and 

 figured in Major Mitchell's Australia, (Vol. ii. 

 pi. 38, p. 131,) and the individual described 

 is preserved in the Colonial Museum, at Syd- 

 ney, N. S. Wales, (No. 35 of Mr. Geo. Ben- 

 nett's Catalogue.) 



It would appear that the two outer toes of 

 the fore foot, which are always very small in 

 the true Bandicoots, are entirely deficient in 

 the Cheer-opus, unless some rudiments should 

 exist beneath the skin ; at all events only two 

 toes are apparent externally ; but they are so 

 developed and armed as to be serviceable for 

 burrowing or progression. The inner toe is 



wanting on the hind-foot. Dental formula : 



. 4 ^ ^ i 



Incisors, _ -; canines, -; pra> 



Fig. 85. 



33 



1 1 



molars, 



33 



molars, 



44 



= 46. 



33 



All the teeth are of small size ; the canines 

 resemble the spurious molars in size and shape, 

 and these are separated by intervals, as in Alur- 

 mecobius. The marsupium opens downwards 

 in the Cfiaropus, as in the true Bandicoots. The 

 species described has no tail. The genus 

 would seem by its dentition to rank between 

 ]\lyr>iiecobius and Perameles. Its digital cha- 

 racters are anomalous and unique among the 

 Marsupialia, but are evidently a degeneration 

 from the Sahatorial or Bandicoot type. 



y. Scansoria. 

 Genus DIDELPI1YS, (Opossums,/g. 85.) 



These Marsupials are now exclusively con- 

 fined to the American Continents, although 

 the fossil remains of a small specie* attest their 

 former existence in Europe contemporaneously 

 with the Palaothere, Anoplothere, and other 

 extinct Pachyderms, whose fossil remains cha- 

 racterize the Eocene strata of the Paris Basin. 

 The dental formula of theGenus Didvlphys is, 



T . 5 5 1 1 



Incisors, -; canines, ; prae- 



molars, 



44 

 33 



molars, 



= 50. 



33 44 



The Opossums resemble in their dentition the 



Didelphyi Virginiana. 



Bandicoots more than the Dasyures : but they 

 closely resemble the latter in the tuberculous 

 structure of the molars. The two middle in- 

 cisors of the upper jaw are more produced than 

 the others, from which they are also separated 

 by a short interspace. The canines are well de- 

 veloped ; the upper being always stronger than 

 the lower. The false molars are simply conical, 

 but are more compressed than in the Carnivo- 

 rous Marsupials. The posterior false molar 

 is the largest in the upper jaw ; the middle one 

 is the largest in the lower jaw ; the anterior 

 one is the smallest in both jaws. The true 

 molars are beset with sharp cusps which wear 

 down into tubercles as the animal advances in 

 age. The crowns of the upper molars present 

 a triangular horizontal section : the base of the 

 triangle is turned forward in the posterior mo- 

 lar ; and obliquely inwards and outwards in 

 the rest. In the lower jaw the true molars are 

 narrower and of more equal size than in the 

 upper jaw: there are five tubercles on each, 

 four placed in two transverse pairs, the anterior 

 being the highest, and a fifth forming the 

 anterior and internal angle of the tooth : the 

 anterior and external angle seems as if it were 

 vertically cut oft'. 



The smaller species of Didelphis, which are 

 the most numerous, fulfil in South America 

 the office of the insectivorous Shrews of the 

 old Continent. Their external resemblance is 

 so close that some have been described as spe- 

 cies of Sorejc, but no true representative of 

 this placental genus has hitherto been disco- 

 vered in South America. The larger Opossums 

 resemble in their habits, as in their dentition, 

 the Carnivorous Dasyures, and prey upon the 

 smaller quadrupeds and birds, but they have 

 a more omnivorous diet, feeding on reptiles 

 and insects and even fruit. One large species, 

 (Did. cancrivora) prowls about the sea- 

 shore and lives, as its name implies, on crabs 

 and other crustaceous animals. Another spe- 

 cies, the Yapock, frequents the fresh waters, 

 and preys almost exclusively on fish. It has 

 all the habits of an Otter; and, in consequence 

 of the modifications of its ffet, forms the type 

 of the sub-genus Chcironcctes, III. Besides 

 being web-footed the anterior extremities pre- 

 sent an unusual development of the pisiform 

 bone, which supports a fold of the skin, like 

 a sixth digit; it has indeed been described, as 

 such, by M. Temminck : this process has not, of 

 course, any nail. The dentition of t!:e Yapock 

 resembles that of the ordinary Didtlfihix. All 

 the Opossums have the inner digit of the hind 

 foot converted by its position and development 



