ITS DISPUTED AFFINITY. 415 



invariably a transverse direction, by which it is locked in the 

 glenoid cavity of the upper jaw, thus constituting a pivot 

 like that of a pair of scissors, which constrains the blades to 

 a vertical motion. In Plagiaulax all these conditions are 

 reversed, the condyle being convex, with its long diameter 

 disposed subvertically ; regarded endwise, it is narrow in 

 proportion to the height, and the outline is ovate or pyriform, 

 the broad end being uppermost. This is a form which is 

 unknown among the Camivora, but common in the Placental 

 Rodents, with the difference, however, that in the latter, the 

 condyle having to work backwards and forwards in a groove, 

 its articular surface is disposed longitudinally. In the com- 

 mon Norway Rat, the articular surface of the condyle is 

 partly vertical, with the pyriform outline of Plagiaulax, but 

 more compressed ; and in one of the American Marmots 

 (No. 2,259, Mus. R. Coll. of Surgeons) it still more closely 

 resembles that of the fossil genus. I cite these instances to 

 show the undercurrent of Rodent analogy which pervades the 

 jaw of Plagiaulax throughout. But a more conclusive and 

 irresistible case of correspondence can be adduced in the 

 condyle of the Aye-Aye. In the words of the celebrated 

 French anatomist who first settled the affinities of the genus, 

 ' La forme generale de la machoire inferieure de 1' Aye-Aye 

 denote une partie forte, large, ou mieux haute et tres-com- 

 primee ; la branche horizontale beaucoup plus longue que la 

 verticale, qui est presque dans la meme direction. Le condyle 

 qui termine cette branche verticale, dans les autres animaux, 

 est droite ici, et presque a l'extremite posterieure de toute la 

 machoire,' &C. 1 The condyle of the Aye-Aye has the same 

 ovate form as that of Plagiaulax, but reversed, the narrow end 

 being uppermost (PI. XXXIV. fig. 13) ; the articular surface 

 is broader and somewhat flatter than in that genus, but the 

 direction of the greater axis is the same, that is, longitudinal 

 and subvertical. 2 The glenoid surface of the upper jaw is 

 modified in correspondence — being broad and flat, and placed 

 on an inclined plane that would intersect the tips of the 

 nasals and the middle of the occipital foramen. Here, then, 

 is a signal failure in the chain of physiological deductions 

 requisite to prove that Plagiaulax was a marsupial carnivore. 

 Next, as regards the depressed position of the condyle — 

 below the level of the grinding- teeth. The author of ' Pa- 

 lseontology ' states that it is a ' character unknown among 



1 De Blainville, ' Ostdographie: ' M6- 

 nioire sur 1' Aye- Aye, p. 19. 



2 'La machoire inferieure, eomme 

 celle des autres rongeurs, se meut evi- 



demment au moyen d'un condyle longi- 113.) 



tudinal, de maniere a empecher tout 

 mouvement horizontal, si ce n'est de 

 l'arriere a, l'avant et vice versa.' (Sand- 

 with, Zoological Proceedings, 1859, p. 



