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 Sciurus 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 ‘Ostéographie’ (Lemur, pl. 5) do not belong to that animal: the 
calcaneum and naviculare exhibit the excessive length characteristic of Tursius 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 Lemuride, 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 ‘Régne 
Animal,’ ed. 1817, pl. 1. 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 scaphoide et calcaneum sont prolongés de 
maniere 4 donner 4 leur tarse autant de longueur qu’a celui de certains oiseaux.’”’—‘ Ossemens Fossiles,’ 4to, 
tom. ili. 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 ‘ Ostéographie des Lemurs,’ pl. 5, and requested him to oblige me 
by inspecting 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 vérifier dans les galeries du Mus¢um de Paris le 
point relatif il Aye-aye que vous m/aviez indiqué. Je n’ai malheureusement pas pu retrouver le tarse figuré dans 
POstéographie, et que M. Laurillard supposait proyenir de l’Aye-aye ; mais une patte postérieure de la méme 
espéce, tirée du sujet donné 4 la collection par M. de Castelle, ne laisse aucun doute. Comparée & la figure 
publice dans le Fascicule des Lémurs, elle montre des différences analogues 4 celles que vous m’avez vous-méme 
fait remarqué. J?ai examiné ensuite, ainsi que nous en étions convenu, la peau bourrée de l’exemplaire de 
Sonnerat. Les deux pattes de derritre n’ont point été touchées, et leurs parties osseuses, les deux tarses 
compris, y sont encore en place. I] n’en est pas de méme du Galago erassicaudatus ; Vindividu encore unique 
que l’on a conserva, et qui est celui décrit par G. Cuvier et E. Geoffroy, n’a plus son tarse gauche, quoique les 
phalanges et les métatarsiens du méme cété soient restés dans la peau, et que la patte droite soit absolument 
M 2 
