42 PROFESSOR OWEN ON THE AYE AYE. 
close, with a slit almost transverse, 74 lines (0'016) long, with the outer canthus higher 
than the inner one, and the plane of each opening inclines a little outward. There is 
a large nictitating fold at the inner canthus. 
The muzzle is short, but deep,—the peculiarly developed incisors and their sockets, 
with the concomitant deep ‘ symphysis mandibule,’ giving it great vertical and small 
transverse extent ; the latter character is heightened by contrast with the great 
expansion of the head to the setting-on of the ears, which expansion suddenly begins with 
the outspanning of the fore part of the zygomata, supporting the thick masseter muscles. 
The fore part of the ‘rictus oris’ is very narrow, and the whole extent to the angles, 
following the semi-elliptical curve which it makes, does not exceed 24 inches. The 
opening of the mouth, in profile, is straight, and scarcely an inch in length. The lips 
have an obtuse but not prominent border ; they increase a little in thickness at the 
angles of the mouth; the inner surface is smooth, with a fuscous pigment. The upper 
lip is short or shallow; it is connected at its fore and inner part by a kind of frenum 
or fold of the inner membrane, which extends into the basal interspace of the upper 
incisors: a few short black whiskers project from it. The interspace between the 
lower lip and the mandible is much deeper, extending below the frenal fold that 
penetrates the basal interspace of the lower incisors ; from the margin of the lower lip 
to the reflexion of its smooth inner skin upon the incisive alveoli measures 9 lines. 
There is a slight protuberance of an oblong form from the inner part of each side of the 
lower lip. The short fine hairs or down of the lower lip, gradually gaining length as 
they recede from the lip-border, are of a lighter grey than those of the upper lip. From 
amongst them there project a few scattered longer hairs, also increasing in length as 
they approach the chin, where a few of the longest form black whiskers, the others 
retaining the greyish tint. 
The naked end of the nose, pink-coloured in the living animal, is of a triangular form 
(Pi. XXII. fig. 4), including the nostrils, which, from their inner rounded and wider part, 
curve slitwise upward and outward to the corresponding angles of the naked space. 
This is impressed by a median and two lateral grooves which meet upon the middle of 
the upper lip, at its frenum within the mouth. The lateral less deep grooves begin at 
the lower and wider part of the nostrils. There may be also seen a feeble linear impres- 
sion extending across the end of the nose from between the inner and lower ends of the 
nostrils. The concavity, directed upward and inward, of the obliquely curved nostrils is 
formed bya slight prominence of an obtuse ‘ala,’ which does not quite touch the thick, 
rounded lower and outer border of the aperture. The breadth of the nose is 11 lines 
(0-024) ; the length of the nostril 53 lines (0°011) ; between the upper ends of the 
nostrils measures, in a straight line, 7 lines (0°015) ; between their lower ends, 3 lines 
(0°006) ; from the lower end of the nostril to the mouth is 3} lines (0°007), The fine 
silky hairs at the circumference of the naked tract commence very short, and gradually 
lengthen as they recede therefrom. Many longer hairs project through the down, 
