446 



PLAGIAULAX. 



any herbivorous or mixed-feeding animal.' I again refer my 

 reader to the figure (PL XXXIV. fig. 13) 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 Becklesii ; 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 



For my reasoning as regards the signification of the long 

 neck or pedicle of the condyle, I refer the reader to my 

 former communication (antea, pp. 419 and 424). It is there 

 stated that the low position of the condyle ' is counter- 

 balanced by another character, of which, so far as I am 

 aware, there is no example among any of the predaceous 

 genera, either placental or marsupial, recent or fossil, namely, 

 the long neck and horizontal jjrojection of the condyle behind 

 the coronoid,' &c. ; and further on I added that the ' arrange- 

 ment is equally without a parallel among the herbivorous or 

 omnivorous tribes.' This latter remark was premature. I was 

 then acquainted with the Aye-Aye only through the figures 

 given by De Blainville, 2 in which the lower jaw is shown 

 in apposition with the skull, thus concealing the coronoid, 

 and its relation to the condyle. But if the accompanying 

 figure (PL XXXTV". fig. 13) of the lower jaw detached be re- 

 ferred to, it will be seen that the condyle is not only below 

 the level of the grinding plane, but that it is projected a long 

 way behind the posterior edge of the coronoid, exactly as in 

 Plagiaulax, and on the same plan of construction — the sole 

 difference being that the sigmoid notch is shallow in the 

 Aye- Aye, and deeply excavated in Plagiaulax. If the notch 

 were deepened in the former, by removing the plate of bone 

 behind and below the posterior edge of the coronoid, in the 

 maimer indicated by the dotted line (/), the resemblance 

 would be complete. In order to place these facts of agree- 

 ment beyond question, I give the following measurements of 

 the relative proportions of the lower jaw in the Aye-Aye and 

 P. Becklesii 3 :— 



1 In some of the families of the Ro- 

 dentia the condyle is barely elevated 

 above the grinding plane of the molars. 

 See De Blainville ' Osteographie : genus 

 Cavia,' PI. ii. Figs. Cavia Cobaya and 

 C. Capybara; genus Hystrix, PI. ii., and 

 Sciurvs maximus, PI. i., while in others, 

 e.g. Castor, both condyle and coro- 



noid are well raised above the same 

 plane. 



2 Osteographie : genus Lemur, PI. v. 



3 It must be borne in mind that fig 1 of 

 my previous communication (PL sxxiii. 

 fig. 1), from which the measurements of 

 P. Becklesii are taken, is magnified two 

 diameters ; the dimensions are therefore 



