PURBECK FORMATIONS. 101 



specimen of Aye-aye, and then turns upon me the weapon with which I had furnished 

 him.' " The author of ' Palaeontology' states that it is a " character unknown among any 

 herbivorous or mixed-feeding animal." " I again refer my reader," pursues Dr. Falconer, 

 " to the figure (fig. 20) of the lower jaw of the Aye-aye. In it the articular surface of the 

 condyle, although directed subvertically, or at the most diagonally, is wholly below the 

 grinding plane of the molars. It looks still more depressed in Plagiaulax BecMesii ; but 

 this is, in part, owing to the. inflected margin of the angle being broken off" in the fossil, 

 while it is entire and salient in the recent form, thus elevating the condyle above the lower 

 plane of the ramus, and leading to an appearance of a greater amount of difference than 

 exists in nature." ^ 



1 will presently refer to the grounds assigned for concluding Cheiromys to be a 

 herbivorous or mixed-feeding genus ; and, referring to the description of the mandible in 

 Plagiaulax BecMesii (p. 77) for the evidence of non-extension of the angle beyond the lower 

 end of the condyle in that species, I will now offer a few remarks bearing upon the relative 

 value of the molar teeth, and the position of the condyle of the mandible in the interpretation 

 of the habits and food of an extinct Mammal. 



Position of condyle relates to the force with which the mandible is worked, shape and 

 pedunculation of the condyle to the direction of the working force. 



The flattened or less convex articular surface favours the rotatory movements ; the more 

 convex, especially transversely extended, and pedunculate or subpedunculate condyle 

 indicates the ginglymoid articulation with greater extent of divarication or wider gape, and 

 more habitual movements in one plane, or limited more or less thereto. The rotatory 

 grinding movements of the mandible are commonly associated with a high position of the 

 condyle and vegetable diet ; the vertical biting movements are commonly associated with 

 a low position of the condyle and animal diet. But the advantage of a long lever afforded 

 by a lofty coronoid process and low-placed condyle may co-relate with powerful biting and 

 gnawing actions, as in the working of the maximised scalpriform teeth of Cheiromys. 



These instruments are wielded by the powerful and favorably formed jaw with a force 

 which enables the Aye-aye to rapidly erode or gouge away the hardest timber. To infer it 

 to be a vegetable-feeder from the scalpriform teeth, and the associated low condyle, and 

 other mandibular modifications, is to assume the ligneous fibre to be gnawed by the animal 

 for food. But, were the species extinct, the molar teeth would teach that this could not be ; 

 few, small, flat-crowned, or tuberculate, they plainly point to operations on nutritive 

 substances from the animal kingdom. 



A captive Aye-aye, it is true, endured a regimen of rice for two months before it died. 

 And this fact is cited to prove it to be a herbivore !^ 



' ' Memoir on Aye-aye,' op. cit., pi. xx, figs. 7, 9 ; ' Palaeontological Memoirs,' vol. ii, pi. 34, fig. 13. 



2 ' Quarterly Jouroal of the Geol. Soc.,' vol. xviii (1862), p. 361 ; also, ' Palaeontological Memoirs and 

 Notes,' 8vo, 1868, vol. ii, pp. 445,446. 



3 " One of the live specimens procured by Sonnerat lived in captivity two months fed on boiled rice. 



