100 FOSSIL MAMMALIA OF THE 



Moschus, we should be justified, if we knew that animal solely by its petrified jaws and 

 dentition, in concluding that its canines, notwithstanding their formidable development 

 and their position as " held well apart," with " the points of penetration doubled, the 

 dilacerating and killing powers multiplied," ' were, nevertheless, not used for predaceous 

 ends, but merely as weapons of sexual combat and defence. Similarly, a reference to the 

 molars of Plagiaulax and Thylacoleo teaches that the approximate laniaries, " placed colla- 

 terally in the axis of the jaws, one on each side, above and below,"" were related to 

 carnivorous habits. 



As beautiful as they are true are the laws of correlation rightly discerned. With the 

 carnivorous type of dentition of Plagiaulax are associated the characters of the carnivorous 

 type of mandible (fig. 12). With the herbivorous teeth of Hi/psiprgmnus go the high-placed 

 condyle, the small sloping coronoid, and the extension of jaw below the condyle for adequate 

 implantation of the pterygoid muscles chiefly concerned in the working of molars framed 

 for grinding vegetable substances (figs. 13 and 14). 



In my memoir on the Aye-aye I had to note that the mandibular condyle was " sessile, 



narrow, rather long, convex both across and 



^^^- '^- lengthwise, and placed on the level of the 



/^^ik grinding teeth," and I remarked that " the 



^j^^^"^^^ (^it. \ *" • sessile condyle contrasts strongly with the 



^E. ""^/ll^^X 1^^ y] pedunculate one, especially in the small ex- 



^\v '^-x v\ Y\ ^ — 7 / *'"^'^'' ^^'■"^^^ {Plagiaulax and Triconodoii) of 



W>' AV^ — / / the Purbeck beds, a concomitant difference 



' ^^^?>^ ^.--Tir being shown in the dentition ; trenchant 



-.^ .■: ..f. - .>^ teeth, grooved as in the lower carnassials of 



Cheiromy.: mandil.le and teetli, the incisor exposed: nat. Tkylacolco, take tllC plaCC of the flat-CrOWUcd 



size. 



molars of Cheiromi/s." 

 Prior to tliis discovery no such low position of the mandibular condyle was known, "iu 

 any herbivorous or mixed-feeding Mammal," supposing the Aye-aye to be such. 



De Blainville had stated that the condyle was " nearly at the posterior extremity of the 

 entire jaw,"* and he might have affirmed it to be quite there ; but of its relative position to 

 the alveolar series neither the text gave information, nor did the figure of the skull with the 

 co-articnlated mandible ])ermit of a certain conclusion on that point. Dr. Falconkr 

 reproducing the same view of the detached mandibular rauuis of Ckeiromys which I 

 had given in pi. 20, figs. 7, 8, of my memoir (see fig. 19), omits any notice of that 

 figure. He cites only the work which I published the year before I received the unique 



' Falconer, ' Quarterly Journal,' &c., p. 352, ' Palaeontological Memoirs,' p. 435. 



- lb., lb., p. 352; ib., p. 435. 



' 'Transactions of the Zoological Society of Loudon,' vol. v, pt. 2, 4to, 18(j3 (read Jauunry 14 and 

 2S, 1862), pp. 50, 81. 



* "Presque 2i Texlremite postcrieure de toute la niachoire," ' Osti^ngrapliie, Memoire sur I'Aye-iiye,' 

 p. 19. 



