260 



MARSUPIALIA. 



cogale. 



fications, according to which the species may general external form and bushy tail, it offers 

 be arranged into gressorial, saltatory, and scan- an especial approximation to the genus 1 



sorial groups. 



a,. Gressoria. 

 Genus MYRMECOBIUS. 



The only known existing representative of 

 this family is the animal described by Mr. 



@. Sahatoria. 

 Genus PERAMELES. (Bandicoots, Jig. 84.) 



Fig. 84. 



Waterhouse, which constitutes the type of his 

 genus Myrinecobius, and of which the following 

 is the remarkable dental formula. (Fig- 83.) 



Fig. 83. 



Myrmecobiiis fasciattu. 



44 11 



Incisors ; canines 1 ^ ; praemolars 



33 6 6 



molars - j; : = 54. 



33' 



66 



From this formula it will be seen that the 

 number of molars, eighteen in both jaws, ex- 

 ceeds that of any other known existing mar- 

 supial, and nearly approaches the peculiar 

 dental formula of the extinct Thylacotherittm,* 

 and that which characterizes some of the ex- 

 isting Armadillos. The resemblance to the 

 genus Dasypus is further carried out in the 

 small size of the molar teeth, their separation 

 from each other by slight interspaces, and their 

 implantation in sockets, which are not formed 

 upon a well-developed alveolar ridge or process. 

 The molars, however, present a distinct multi- 

 cuspidate structure, and both the true and 

 false ones possess two separate fangs, as in 

 other Marsupials. The inferior molars are 

 directed obliquely inwards, and the whole 

 dental series describes a slight sigmoid curve, 

 (Jig. 97.) The false molars present the 

 usual compressed triangular form with the 

 apex slightly recurved ; and the base more or 

 less obscurely notched before and behind. The 

 canines are very little longer than the false 

 molars ; the incisors are minute, slightly com- 

 pressed and pointed ; they are separated from 

 each other and the canines by wide intervals. 



The Myrmecobians are insectivorous,f and 

 shelter themselves in the hollows of trees, fre- 

 quenting most, it is said, those situations where 

 the Port-Jackson willow abounds. In the 

 structure and proportions of its hinder feet, 

 Myrinecobius resembles the Dasyurine family ; 

 and in the slightly developed canines, the 

 smooth external surface of the skull, the 

 breadth between the zygomata, and the absence 

 of the interparietal ridges, as well as in its 



* This small Tnsectivore, of which the marsu- 

 pial character is doubtful, had twenty-four molars 

 in each jaw. See Geol. Trans. New Series, vol.vi. 

 part 1. 



t Mr. Gould informs me that they feed exclu- 

 sively on ants. 



Perameles nasuta. 



55 11 . 



Incisors ^; canines ^ ^> prsemolars 



33 44 



-; molars ^z^- = 48. 



This dental formula characterizes a number 

 of Marsupials commonly known in Australia 

 by the name of Bandicoots; the hind legs are 

 longer and stronger than the fore, and exhibit 

 in a well-marked manner the feeble and slender 

 conditions of the second and third digits 

 counting from the inside, and the sudden in- 

 crease in length and strength of the fourth and 

 fifth, or two outer toes, which are chiefly sub- 

 servient to locomotion. In consequence of the 

 inequality of length in their extremities the 

 mode of progression in the Bandicoots is by 

 bounds, the hind feet being moved toge- 

 ther, and alternately with the fore feet, 

 as in the hare and rabbit, and the crupper is 

 raised higher than the fore-quarter. The teeth 

 which offer the greatest range of variation in 

 the present genus are the external or posterior 

 incisors and the canines : the molars, also, 

 which originally are quinque-cuspidate, have 

 their points worn away, and present a smooth 

 and oblique grinding surface in some species 

 sooner than in others. 



The Bandicoots which approach nearest to 

 the Myrmccobius in the condition of the in- 

 cisive and canine teeth, are the Perameles obe- 

 sula and P. Gunnii. There is a slight interval 

 between the first and second incisor, and the 

 outer or fifth incisor of the upper jaw is sepa- 

 rated from the rest by an interspace equal to 

 twice its own breadth, and moreover presents 

 the triangular pointed canine-like crown which 

 characterizes all the incisors of Myrmecobins ; 

 but the four anterior incisors are placed close 

 together and have compressed, quadrate, true 

 incisive crowns. From these incisors the canine 

 is very remote, the interspace being equally 

 divided by the fifth pointed incisor, which the 

 canine very slightly exceeds in size. In Peram. 

 nasuta the incisor presents the same general 

 condition, but the canines are relatively larger, 

 In Per. Gunnii, the outer incisor is closer to 

 the others, which it also more nearly resembles 

 in form than in the preceding species; but in 

 Per. Lagotis, it is not separated from the rest 

 by a wider interval than that which intervenes 

 between the first and second incisor. In both 



