PROFESSOR OWEN ON THE AYE-AYE. 83 



Structure and proportions of the tarsus ; but the inner part of the naviculare, which 

 articulates -with the backwardly produced angle of the ento-cuneiforme, is a distinct bone 

 in Sciunts as in other pentadactyle Rodents : in Castor the dismembered part of the 

 naviculare articulates with a larger proportion of the ento cuneiforme, and there is a 

 second accessory ossicle on the radial side of the tarsus. But the size, shape, and 

 position of the articular surface for the hallux still further differentiate the ento-cunei- 

 forme in Chiromys from that in any Rodent, relating as it does to the capital distinction of 

 the opposable hinder thumb, which unites the Aye-aye with other Quadrumana. In the 

 relative length of the tarsus to the leg and to the rest of the foot, the Chiromys most 

 resembles Lichanotus and Propithecus : it is rather shorter than in Lemur proper, being 

 less than one-third the length of the tibia, and only about one-fourth the length of the 

 whole foot. The scaphoid and calcaneum are proportionally rather shorter than in 

 Lemur proper or Perodicticus, Btt. The bones figured as tarsal ones of the Aye-aye 

 in De Blainville's ' Osteographie ' {Lemur, pi. 5) do not belong to that animal : the 

 calcaneum and naviculare exhibit the excessive length characteristic of Tarsius and 

 Otolicnus', and agree in size, as do likewise the tibia and fibula of the same plate, 

 with those bones in Otolicnus crassicaudatus, Wagn.^ The sum of the osteological com- 

 parisons favours the affinity of Chiromys with the LemuridcB, and with that section 

 having the less elongate tarsus. 



Comparison of Muscles. — Although, in a comparison of the Quadrumana with their 

 conterminous Gyrencephalous order, the Carnivora, the size and distinctness of the 

 clavicular portion of the sterno-cleido-mastoideus, in Chiromys, shows its resemblance to 



' Otolicnus crassicaudatus, Wagner, or ' Grand Galago,' of which Cuvier figures the skin in his ' Regne 

 Animal,' ed. 1817, pi. l.fig. 1, from which specimen the bones, supposed to belong to the Aye-aye, had probably 

 been taken ; and it might be from the examination of this very specimen that Cuvier was enabled, for the first 

 time, to make known that, " Dans les Tarsiers et les Galagos, les os scapho'ide et calcaneum sont prolonges de 

 maniere a donner a leur tarse autant de longueur qu'a celui de certains oiseaux." — 'Ossemens Fossiles,' 4to, 

 torn. iii. p. 508 (1822.) 



^ [Prof. Gervais, of Montpellier, having visited the British Museum since the first sheets of the present 

 memoir went to press, I communicated to him my suspicion as to the origin of the tarsal bones figured by 

 De Blainville as those of the Aye-aye, in his ' Osteographie des Lemurs,' pi. 5, and requested him to oblige me 

 by inspectmg the stuffed specimens of the Aye-aye and Galago on his return to Paris. The following is the 

 reply with which I have been favoured by the accomplished Professor : — 



" MoN CHER CONFRERE, — C'est hier seulement que j'ai pu verifier dans les galeries du Museum de Paris le 

 point relatif a 1' Aye-aye que vous m'aviez indique. Je n'ai malheureusement pas pu retrouver le tarse figure dans 

 1' Osteographie, et que M. Laurillard supposait proveuir de 1' Aye-aye ; mais une patte poste'rieure de la meme 

 espece, tire'e du sujet donne a la collection par M. de Castelle, ne laisse aucun doute. Compare'e a la figure 

 publiee dans le Fascicule des Lemurs, elle montre des differences analogues a celles que vous m'avez vous-meme 

 fait remarque. J'ai examine ensuite, ainsi que nous en ^tions convenu, la peau bourree de I'exemplaire de 

 Sonnerat. Les deux pattes de derriere n'ont point ete touch&s, et leurs parties osseuses, les deux tarses 

 compris, y sont encore en place. II n'en est pas de meme du Galago crassicaudatus ; I'iudividu encore unique 

 que Ton a conserva, et qui est celui decrit par G. Cuvier et E. Geoffrey, n'a plus son tarse gauche, quoique les 

 phalanges et les mdtatarsiens tlu meme cote' soient restes dans la peau, et que la patte droite soit absolument 



M 2 



