PROFESSOR OWEN ON THE AYE-AYE. ' 57 



the first (»i 1) is the narrowest ; in this and the second the implanted base is divided into 

 an anterior and posterior root (fig. 9) ; it remains simple in the last (m 3). The longest 

 diameter of the mid-molar does not exceed 2 lines ; these teeth are, therefore, very 

 small in proportion to the incisors, and the molar series is singularly small in proportion 

 to the entire skull and body of the Aye-aye'. 



The very compressed form of the incisors, the obliquity of their narrow working 

 surface allowing the enamelled ends only of the upper and lower pair to come into con- 

 tact, gives almost a pointed form to those ends, which are thus adapted to pare away 

 very narrow strips of the bark and the wood they may be operating on ; whilst the 

 great fore-and-aft breadth of the incisors, and the angle at which their front or 

 enamelled borders converge in each pair, adapt them to penetrate deeply and quickly 

 into the substance of a bough. In all these characters their special adaptation to the 

 work of exposure of the slender canals of the wood-boring caterpillars becomes very 

 obvious. The length and curved implantation of the teeth, and the provision for their 

 perpetual renovation, are conditions of equal fitness for the daily repetition of such 

 eroding operations. By these adaptive modifications the front teeth of the Aye-aye 

 doubtless resemble in their broader features the scalpriform incisors of the true Rodents ; 

 but to infer that, therefore, the food of the Aye-aye was similar, and that it subsisted, 

 like the Squirrel and Beaver, e.g., on the coarser vegetable products, would be as falla- 

 cious as to conclude, from the shape and proportions of the canine teeth in the male 

 Troglodytes, that the Gorillas and Chimpanzees were flesh-eaters. The diet is best 

 indicated by the molars ; and the functions of specially developed teeth in a state of 

 nature are made known by observations on living animals. The true relations of the 

 dental characters by which the highest Quadrumane resembles a Carnivore, and the lowest 

 one resembles a Rodent, are elucidated by the totality of their organization respectively 2. 



§ 5. Muscles. 



In this section I restrict myself to a description of those parts of the muscular system 

 which seem to throw most light on the affinities of Chiromys, and my remarks chiefly 

 relate to the muscles of the limbs. 



The platysma myoides (PI. XXII. fig. 1, s)is well developed, covering all the muscles 



' Since this sheet was in type, I have learnt from Prof. Gervais, of MoutpeUier, that the jaws of a young 

 Chiromys, presented by M. de Lastelle to the Museum of Natural History, Paris, exhibit a molar anterior to the 

 three in the lower jaw, corresponding to, but smaller than, the anterior one above. In this immature specimen, the 

 last of the three true molars has not cut the gum. By the time this takes place, the first small molar is shed in the 

 lower jaw : it is retained in the upper one : it may be a deciduous or milk-molar, d 4 instead of p 4, in both 

 jaws. M. Gervais has figured this phase of dentition in his ' Histoire Naturelle des Mammiferes,' vol. i. p. 176. 



" The following is the result of a microscopic examination kindly undertaken by my friend James Salter, Esq.,' 

 F.L.S., of the teeth of the Chiromys : — " The transverse section of the Aye-aye's incisor is singularly like the 

 outline of a vertical section of the lower cuspidatus of man, the outer surface of the former corresi)ondiiig 

 with the^oreiof the latter. The enamel is thick and hard ; it clothes the tooth on the outer surface by about 



VOL. V. PART II. I 



