436 



PLAGIAULAX. 



thick root in the fore-part of the jaw, like the large lower 

 incisor of a Kangaroo 1 or Wombat.' But the shape of the 

 tooth prevailed in deciding him to pronounce it carnivorous. 

 Now, the form differs in the two species ; and I ask any 

 Comparative Anatomist to look at fig. 2 of PI. XXXIV., and 

 say whether the tooth there represented is formed to pierce, 

 retain, and kill — being the attributes with which Professor 

 Owen invests the incisor of P. Becklesii. It is projected for- 

 wards with a slight upward inclination, somewhat as in the 

 vegetable- feeding Koala (Phascolarctus cinereus). The incisor 

 of P. Becklesii 2 is undoubtedly curved more decidedly upward ; 

 and, when viewed sidewise, it is not very unlike a canine. 

 But the same may be said equally of the lower incisor of the 

 Lemurine Aye-Aye (PI. XXXIV. figs. 13 and 14). In this re- 

 markable form, the affinities of which were so keenly disputed 

 by the great French anatomists, Cuvier and De Blainville, 

 the solitary incisors are collateral, on the Rodent type ; com- 

 pressed laterally, and very deep at the base, they sweep up- 

 wards in a bold curve, being scooped vertically behind, to 

 terminate in a sharp edge ; so that, regarded sidewise, so far 

 as vertical direction goes, they are more canine-like than in 

 either species of Plagiaulax. But the resemblance goes no 

 further. In the former the incisor, which is only partially 

 invested with enamel, is continued backwards below the 

 molars, the pulp-nucleus being persistent, and the chisel- 

 shaped edge is constantly maintained by use 3 — conditions 

 which are wanting in the latter. Should the construction of 

 the skull and other parts of the skeleton of P. Becklesii be 

 ever discovered, there is little doubt that modifications will 

 be detected throughout in conformity with those of its in- 

 cisors, as in the felicitous instance, cited by Cuvier, of the 

 secret relation between the upper canine-shaped incisors of 

 the Camel and the bones of the tarsus ; this exceptional 

 character does not remove the Camel from among the 

 Ruminants, nor does the form of the incisor of P. Becklesii 

 appear to me to be of sufficient weight to counterbalance 

 the clear evidence of a phytophagous and rodent plan of 

 construction. 





1 Encyclop. Brit. 8th edit. vol. xvii. 

 p. 161. ' Shrew and Wombat' are sub- 

 stituted in the ' Palaeontology,' p. 353. 



2 PL xxxiii. fig. 1. 



3 De Blainville asserts that the in- 

 cisors of the Aye-Aye are invested all 

 round with a shell of enamel, and that 

 the posterior facet is not the result of 

 wear (Memoirs sur 1' Aye-Aye, p. 23) ; 

 while Dr. Sandwitb, in his interesting 



account of the habits of this animal, 

 affirms that the facet is denuded, as in 

 the Eodents (Zool. Proc. Feb. 22, 1859, 

 p. 111). In a finely preserved cranium, 

 for the transmission of which to London 

 I am, indebted to the great courtesy of 

 M. Edouard Verreaux of Paris, it is 

 distinctly seen that the coat of enamel 

 is limited to a belt which sheathes only 

 the anterior half of the incisors. 



