78 PROFESSOR OWEN ON THE AYE-AYE. 



the idea of its being the homologue of two incisors blended together ; but the 

 larger anterior incisor in Propithecus, usurping nearly the whole of the premaxillary, 

 gives the truer view of the nature of the scalpriform pair in Chiromys. 



The single pair of large inferior incisors, associated, as they are, with the pollicate 

 foot in the Aye-aye, reminds one of the mandibular dentition and feet of the Phalangers ; 

 and if such an approach to the Rodent type be made by these pedimanous marsupials 

 without masking their true lyencephalous affinities, as little need it prevent a recognition 

 of the Lemurine nature of the Chiromys, where a single pair of upper scalpriform 

 incisors is also paralleled by the marsupial Wombat, which offers the same extreme 

 modification of the dentition of its group,^ — a relation which Cuvier seems to intimate 

 by associating the skulls of the two ' anomalous ' quadrupeds on the same plate of the 

 ' R^gne Animal.' 



The incisors, although by their size, curvature, depth of implantation, and structure 

 they most closely resemble the scalpriform teeth of the Rodents, yet they are much 

 narrower in proportion to their depth, or fore-and-aft diameter, than in any known 

 Rodent. In this compressed character they more resemble the first upper incisors of 

 Propithecus, Benn., and the canines of Lemur proper : the shape of the inserted part of 

 the crown is much more laniariform than scalpriform. Nevertheless they are true 

 incisors, like those in Phascolomys, but have less resemblance to those of Rodents than 

 in that marsupial. In both the Wombat and the Aye-aye the exposed parts of both 

 upper and lower incisors project more forward, and meet each other more obliquely, 

 than in the true Rodents, in which their direction is more vertical. The molar teeth, 

 on the other hand, oppose each other more vertically than in the Rodents, and show 

 no inclination to the outward bend of the upper and the inward one of the lower molars, 

 so common in that order. The molar teeth, by their simple coronal cap of enamel, 

 depart still more from the complex Rodent type of these teeth, and manifest their 

 essentially quadrumanous nature. Like Stenops, Otolicnus, and Tarsius amongst the 

 LemuridcB, they are more numerous above than below, in the adult Aye-aye — a difference 

 which is rare and exceptional among the Rodentia. Their fewness and smallness is a 

 speciality in Chiromys among the Lemuridce. The soft, nutritious, readily masticable 

 nature of the food of the Chiromys is indicated by their small size and simple obtuse 

 crowns. A reference to the excellent account of the skull and dentition of Chiromys, 

 given by De Blainville in his ' Osteographie,' will show that I have reproduced most 

 of the comparisons which were there first urged in support of its Lemurine affinities. 

 The opportunity of examining a foetal or very young Aye-aye is much needed to deter- 

 mine the fact of rudimental transitory teeth, between the retained incisors and molars'. 



' The interesting observation by Prof. Gervais, cited at p. 57, had not come under my notice when the above 

 passage was in type : it still leaves the uterine and milk stages of dental development to be determined. 



