*4 
PROFESSOR OWEN ON THE AYE-AYE. 8l 
in all Rodents,—least so, perhaps, in Sciurus; but there is no such convergence in 
Chiromys. The diastema is chiefly in the maxillary, and is sharp, in Chiromys; it is 
chiefly in the premaxillary, and is smooth, broad, and convex, in Rodentia. In this 
order the squamosal is peculiar for its length, its straight upper border, and the detach- 
ment of the zygomatic process from the fore part of the outer side ; it forms a deep longi- 
tudinal groove for the mandibular condyle, and does not anchylose with the petro- 
tympanic element. None of these characters are shown in the squamosal of the Aye- 
aye, which conforms with that in the Lemuride, and more especially departs from the 
Rodent type in the broad flat articular surface for the lower jaw; but this has no 
posterior ridge. A well-ossified palate is an exception in the Rodentia, and the Sciuride 
show best that exception ; but in these the prepalatine or incisive vacuities are longer 
than in Chiromys, and the postpalatine notch is deeper: in the breadth of the bony palate 
the Squirrels come nearest to the Aye-aye. 
The mandibular condyle in Chiromys approaches the form of that in Rodentia by the 
superiority of its fore-and-aft over its transverse diameter; but, in its oval convexity, 
it resembles more nearly the condyle in Tarsius than that of any Rodent. In all 
Rodents the condyle of the mandible is higher than the level of the grinders ; the angle 
of the jaw is produced backwards beyond it ; the long and narrow coronoid process 
curves back to nearly the same vertical line with the condyle. The symphysis reaches 
the lower border of the ramus, and the curved incisive socket projects more or less from 
the inner surface. All these Rodent characteristics of the mandible are wanting in 
Chiromys. In certain Lemuride (Stenops, Lichanotus, Illig., Propithecus, Bntt.) the angle 
of the jaw is rounded off; but it is nearly on a vertical line with the condyle: its 
advanced position in Chiromys is a speciality in the Quadrumanous series. It is one 
which leads it still further from the Carnivora; and the sessile condyle contrasts 
strongly with the pedunculate one, especially in the small extinct Ferines (Plagiaulax 
and Triconodon) of the Purbeck beds: a concomitant difference being shown in the den- 
tition : trenchant teeth, grooved as in the lower carnassials of Thylacoleo, hold the place 
of the thick flat-crowned molars of Chiromys. 
The scapula of Chiromys differs from that of Rodents, and resembles that of Lemurs, in 
the proportions of the supra- and infra-spinal fosse. The subscapular surface does 
not show the intermuscular cristz which are usually so well marked in Rodents. The 
lower border, though well everted, has less the character of a second spine than it shows 
in the Squirrels. 
The perforation above the internal condyle of the humerus is the rule in the Lemuride ; 
it is the exception in the Rodentia. The perforation between the condyles is common 
* in the Rodentia’ ; it is not present in the Lemuride. In the foregoing comparison the 
humerus of Chiromys agrees with that in the Lemuride. In its relative length to the 
* The intercondyloid perforation, without the supracondyloid one, occurs in Leporide, Capybara, Cavia, Doli- 
chotis, Chinchilla, Lagotis, Myopotamus, Celogenys, Dasyprocta, Hystriz, and Arvicola. The supracondyloid 
VOL. V.—PART II. M 
