157 



mandible, and where such condyles are associated, as is the rule, with laniariform not 

 with scalpriform anterior teeth, the condyle is more prominent ; the part of the ascending 

 ramus supporting the condyle curves toward the coronoid process, in a course at first 

 more or less deeply concave, then vertical or recurved ; and a similar well-marked con- 

 cavity divides the condyle from the angle of the jaw, save in the most decidedly zoopha- 

 gous of the Marsupialia (Sarcophilus, Thylacinus, Plagiaulax), in the latter of which the 

 convex condyle forms, as it were, the upper and back part of the angle itself. 



The condyle in Plagiaulax (fig. 10, b) projects a little below the horizontal level 

 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 Sarcophilus, 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 Becklesii (fig. 20 p, p. 178), 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. Falconee states, below the condyle as in the Aye-aye, but to the inner side thereof, 

 as in Sarcophilus, Thylacinus, and Phascolotherium^. 



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. 



* 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. 

 t XI. p. 447. 



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