PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
239 
exposed the nest of a grub, which he daintily picked out of its bed with the slender 
tapping finger, and conveyed the luscious morsel to his mouth. I watched these pro- 
ceedings with intense interest, and was much struck with the marvellous adaptation of 
the creature to its habits, shown by his acute hearing, which enables him aptly to di- 
stinguish the different tones emitted from the wood by his gentle tapping ; his evidently 
acute sense of smell, aiding him in his search; his secure footsteps on the slender 
branches, to which he firmly clung by his quadrumanous members ; his strong rodent 
teeth, enabling him to tear through the wood ; and lastly, by the curious slender finger, 
unlike that of any other animal, and which he used alternately as a pleximeter, a probe, 
and a scoop”*. 
Sonnerat, besides specifying the compulsory food on which his captive Aye-aye 
perished in two short months, not being able longer to sustain life thereon, describes 
the long slender naked middle digit : — “ il s’en sert pour tirer des trous des arbres les 
vers qui sont sa nourriture”f. I understand this to mean that larvae — “ vers” — are its 
natural or staple food. The affirmation may have been made from Sonnerat’s observa- 
tions on Chiromys in a state of nature, or on the reports of natives of Madagascar, or 
on both authorities. It is a better testimony of its natural “ nourriture ” than the com- 
pulsory diet of confinement, and ought to be quoted in a consideration of the present 
important question. 
For to what condition is Comparative Anatomy reduced if we reject the testimony 
which Dr. Falconer does not cite, and admit, upon the testimony he does .cite, that 
Chiromys is a vegetable feeder ! W ere the scalpriform teeth enabled, through the low 
position of a terminal condyle, to gouge out the hard woody fibre for food in order that 
the animal might masticate such fibre X Only upon this hypothesis could Chiromys be 
cited as an exception to the correlation of such position of mandibular joint with animal 
diet. But xylophagous habits involve complex ever-growing molars, like those of the 
Voles, the Beavers, and Capybaras. A reference to the molar teeth of the Aye-aye at 
once indicates its true diet, and the part played by the lower jaw and its chisels in 
obtaining it. Observation of the living animal in its native woods vindicates the 
Cuvierian principle, and gives the rational explanation of both dental and maxillary 
machinery. Instead of being an exception, the low condyle enters into the rule of its 
association with the getting of food of an animal nature. 
Now let us return to the application of the Aye-aye’s mandibular structure to the 
explanation of that in Thylacoleo and Plagiaulax. “ The large front teeth in Chiromys 
are curved in segments of circles, the working surface is elongate, in breadth equalling 
that of the base of the tooth, with a front convex enamelled border, forming the obtuse 
apex of the gouging surface” J. 
* Letter from Dr. Sandwith, quoted in “ Owen on the Aye-aye,” Traus. Zool. Soc. vol. v. pt. 2. 1863, p. 37. 
t Voyage aux Indes Orientales, ifcc., Paris, 4to, 1782, p. 122. 
+ Owen, ‘ On the Aye-aye,’ 4to, 1863, p. 25. 
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