260 MARSUPIALIA. ¥ 
fications, according to which the species may general external form and bushy tail, it off 
be arranged into gressorial, saltatory, and scan- an especial approximation to the genus Ph 
sorial groups. 
a. Gressoria. 
Genus MYRMECOBIUS. 
The only known existing representative of 
this family is the animal described by Mr. 
Waterhouse, which constitutes the type of his 
nus Myrmecobius, and of which the following 
is the remarkable dental formula. ( Fig. 83.) 
Fig. 83. 
, 4—4 . 1 
Incisors 3g? Canines [—7; premolars 
3—3 
=——s; molars >= 54. 
6—6 
a3? 6—6 
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 Thylacotherium,* 
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 
= eg 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, 
(fig. 97.) The false molars present the 
usual eorprenred 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,+ and 
shelter themselves in the hollows of trees, fre- 
uenting most, it is said, those situations where 
the Port-Jackson willow abounds. In the 
structure and proportions of its hinder feet, 
_Myrmecobius resembles the Dasyurine family ; 
and in the slightly develo 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 Insectivore, of which the marsu- 
pial character is doubtful, had twenty-four molars 
in each jaw.—See Geol. Trans. New Series, vol.vi. 
art 1. 
i + Mr. Gould informs me that they feed exclu- 
sively on ants. 
cogale. 
Genus PERAMELES. (Bandicoot 
« 
B. Saltatoria. 
Pea: 
pee 
: VOLE OIA A“ 
Ae 
ae 
Ince Se 
neisors 3-3; canines 7—75 Ff 
3—3 . 4—4 . 
3_3 3 molars 74" == 48. 
This dental formula characterizes a num 
of Marsupials commonly known in Aust 
by the name of Bandicoots; the hind legs) 
longer and stronger than the fore, and exhi 
in a well-marked manner the feeble and slen 
conditions of the second and third ¢ 
counting from the inside, and the sudden 
crease in length and strength of the fourth ¢ 
fifth, or two outer toes, which are chiefly 
servient to locomotion. In consequence of 
inequality of length in their extremities 
mode of p ion in the Bandicoots is 
bounds, the hind feet being moved t 
ther, and alternately with the fore 
as in the hare and rabbit, and the cruppe 
raised higher than the fore-quarter. 
which offer the greatest range of on 
the present genus are the external or poste 
incisors and the canines: the molars, a 
which originally are quinque-cuspidate, ha 
their points worn away, and present a smo 
and oblique grinding surface in some spe 
sooner than in others. 
The Bandicoots which approach nearest 
the Myrmecobius in the condition of th 
cisive and canine teeth, are the Perameles « 
sula and P. Gunnii. There is a slight inte 
between the first and second incisor, ¢ 
outer or fifth incisor of the upper jaw is se 
rated from the rest by an interspace equ 
twice its own breadth, and moreover pr 
the triangular pointed canine-like crown wW 
characterizes all the incisors of Mi ) 
but the four anterior incisors are placed 
together and have compressed, quadrate 
incisive crowns. From these incisors the cai 
is very remote, the interspace being equ 
divided by the fifth pointed incisor, which 
canine very slightly exceeds in size. In Per 
nasuta the incisor presents the same gene 
condition, but the canines are relatively 
In Per. Gunnii, the outer incisor is ele 
the others, which it also more nearly resemb 
in form than in the preceding species; but 
Per. Lagotis, it is not separated from the: 
by a wider interval than that which interve 
between the first and second incisor. In b 
Phe 
oe 
