PEOFESSOE OWEN ON THE FOSSIL MAMMALS OF ATJSTEALIA. 
237 
of the alveolar series ; in Chiromys and Carnivora it is on that level. But if the mandi- 
bular condyle in Plagiaulax agreed in all characters with that of the rodent Lemur, this 
would not show Plagiaulax to be a vegetable feeder. The direct testimony of the insec- 
tivorous or rather larvivorous habits of the Aye-aye is too strong and too sure to be done 
away with by the enforced food on which a captive individual may have been compelled 
artificially to subsist. 
However, for the instruction of any physiologist or palaeontologist who may still deem 
the position of the condyle in Chiromys to throw light upon the food and nature of 
Plagiaulax and Thylacoleo, it may be stated that in every secondary mandibular character 
Plagiaulax differs from Chiromys , and resembles & 'arcophilus, Thylacinus, and Phasco- 
lotherium*. The supporting part of the condyle sinks below the transversely extended 
upper part of the convex articular surface, before curving forward and upward to the 
coronoid, leaving an entering notch between that process and the coronoid which, in 
the type specimen of Plagiaulax Pecklesii (fig. 20 f, p. 258), closely corresponds in form 
with that in Thylacinus and Phascolotherium. 
The fractured line of the angle of the jaw is not beneath the neck of the condyle, but 
on the inner side of the inferior border of the rising ramus passing to the lower end of 
the condyle. That part of the angle which has been broken off did not extend, as 
Dr. Falconer states, below the condyle as in the Aye-aye, but to the inner side thereof, 
as in Sarcojghilus , Thylacinus , and Phascolo thorium f . 
Whoever may have watched a living Thylacine or Ursine Dasyure must have been 
struck with the width of its gape. The extent of such motion of the mandible is due 
to the freedom of the joint (figs. 11, 12, b) and its distance from the moving lever (c). 
The like or even greater relative backward position of the condyle must have equally or 
more favoured “ the power of separating the jaws in front essential to a predaceous 
animal having laniary teeth,” like those of the Thylacoleo and Plagiaulax (fig. 10), “ con- 
structed to pierce, retain, and kill”J. And we have direct proof in the sessile condition 
of the condyle in the Aye-aye that the power of separating the jaws was more restricted 
in that carnivorous and rodent Lemur. 
§ 11. Testimony as to the native food of the Aye-aye. — The advantage to the forcible 
action of the jaw by the backward position of the condyle is recognizable, whether the 
fore teeth of the jaw be fashioned for “biting,” i. e. piercing as a dagger and becoming 
infixed in a prey, or for “ eroding ” hard wood, as a gouge or chisel. 
Modifications of the mandible might be expected to be associated with the different 
actions and applications of the fore teeth, aided or advantaged by the carrying back the 
condyle and lengthening the lever of the biting powers. 
Prior to 1861 such backwarclly placed as well as low-placed condyle was not known 
* British Fossil Mammals, 8vo, 1846, p. 65. 
t It is this “ broad ” part of the condyle which gives it the “ ovate or pyriform outline ” (XI. p. 445). In 
-Thylacinus and Sarcophilus a part of the articular surface also extends down from the back of the condyle. 
+ XI. p. 447. 
MDCCCLXXI. 2 K 
