On 
GENUS OF MARSUPIAL ANIMALS. 153 
mencing with the skull of Thylacinus, and ending with that of Phascogale), we can trace 
in the teeth.a gradual blending of the carnivorous structure into the insectivorous ; and 
as the skulls are modified accordingly, I shall confine my observations to the latter, my 
object being to show that the skull of Myrmecobius differs from that of Phascogale, 
chiefly in those points of structure, to which a gradual approach may be traced through 
species allied to the latter genus. 
In Thylacinus we perceive a great width and strength in the zygomatic arch, a con- 
siderable contraction of the cranial cavity (especially at its posterior part), a great de- 
velopment of the interparietal ridge and an abrupt termination of the skull immediately 
behind the zygomatic arch. In Dasyurus Ursinus the same general characters also 
obtain, but the parietals extend somewhat further back. In Das. Maugei we have still a 
considerable contraction of the skull in the centre of the temporal fossa, but there is a 
much greater lateral development of the parietal bones, indicating a more voluminous 
cavity for the reception of the brain ; they also extend further beyond the zygomatic arch, 
and dilate at their junction with the occipital bone ; the interparietal ridge is also com- 
paratively feeble. In the genus Phascogale this ridge is quite lost, the skull is less 
contracted in the middle, the parietal bones are more developed, and the cranial 
cavity is still more voluminous ; the upper surface of the skull is therefore more evenly 
convex. In the genus Myrmecobius the interparietal ridge is also wanting ; the frontal 
bones are very broad, and together form almost a square, and the cranial cavity exceeds 
that of Phascogale ; the posterior ridge of the orbital margin forms an acute process, 
which is not seen in the last-mentioned genus, but which occurs both in Dasyurus Ur- 
sinus and Thylacinus cynocephalus, although in these species the temporal bones are 
remarkably contracted. The hinder angle of the lower jaw in all these animals is pro- 
duced into an elongated process. 
Although in the structure of the skull the animal here described evinces an affinity 
to Phascogale, it differs from that genus in the want of a thumb to the hind feet, and in 
the strength and larger size of the claws of the fore feet, which are shaped somewhat 
like those in the genus Herpestes, and are evidently suited to burrowing. The fore- 
legs are also stouter in proportion, and the feet are stronger. In their narrow and 
pointed shape, the ears resemble those of Perameles nasutus, and differ from those of 
Phascogale; they also differ in being tolerably well clothed with hairs both externally 
and internally. 
I imagine that in the present animal I can perceive a slight approach to the Edentate 
Marsupialia, or the Monotrémes of Cuvier, and think that, analogically, it may be com- 
pared to the genus Tupaia among the true Insectivora, bearing a somewhat similar con- 
nection with Echidna and Ornithorhynchus, to that which exists between the last-men- 
tioned genus and the genera Erinaceus and Mygale. That there is a greater dissimi- 
larity in structure between the genus Myrmecobius and the Monotrémes, than between 
Tupaia and Mygale, must be allowed ; we are, however, in a measure prepared for this, 
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