fiO PROFESSOR OWEN ON THE AYE-AYE. 



side of the petro-tympanic bulla (ib. is). There is no ridge behind it to prevent the free 

 movements of the mandible backward and forward, accompanying the rodent action of 

 the great scalpriform incisors. The outer facet of the zygomatic process shows a 

 depression in front of the meatus auditorius. 



The mandible (PI. XX. figs. 3, 7, & 9) is short and deep : each ramus is compressed 

 and straight ; they converge at an acute angle to a short ligamentous symphysis. 

 The condyle (x) is sessile, narrow, rather long, convex both across and lengthwise, and 

 the latter most so, looking backward and upward, and placed on the level of the 

 grinding-teeth. The thin borders of the ascending ramus diverge from the condyle 

 as they pass, the one downward and inward to the low angle (figs. 7 & 9, y), and the other 

 forward and upward to the better-marked and more advanced coronoid {ib. z), the obtuse 

 end of which is nearer the last molar (fig. 7, "> 3) than the condyle. Both sides of the 

 postmolar half of the ramus are almost flat. A slight ridge above the angle bounds 

 the surface for muscular insertion behind ; and here the angle is a little inflected. 



The entry of the dental canal (figs. 3, 7, t) is on the line from the back molar to the 

 condyle, but rather nearer the latter. The fore border of the coronoid (z) is almost 

 straight, and slopes forward, parallel with the hind border (y, x) of the ascending ramus, 

 to the outside of the jaw, below the alveolus of the middle molar (fig. 9, »' 2). The 

 lower border of the ramus from the angle undulates, first convex, then concave, finally 

 convex as it curves slightly upward to the alveolar border of the great incisor. The 

 short diastema (figs. 7, 8, d), almost equal to the fore-and-aft breadth of the incisor (i), 

 is concave and sharp. The small single outlet of the dental canal (PI. XIX. 32, 0) is 

 below the fore part of the first molar. The symphysis does not reach to the angle 

 between the anterior and inferior borders of the horizontal ramus. 



The sockets of the three molars occupy an extent of 5^ lines (-0012) : the first and 

 second sockets are divided into two depressions ; the third is a simple oblong-conical 

 cavity. 



The socket of the incisor (fig. 9) has the external border of the outlet sinuous, the 

 internal border convex ; it is very narrow in proportion to its length, and makes no pro- 

 jection on either the outer or inner side of the ramus ; it extends in a regular curve 

 beneath the molar series to the base of the coronoid process, the tooth it contains 

 {'i, p) describing a semicircle. 



Bones of the fore limb.— The scapula (Pis. XIX. 51, XXI. figs. 12, 13) is 2 inches long, 

 with a basal breadth of 1 inch ; the base is straight between the root of the spine and 

 the beginning of the lower angle, but curves forward to that and to the upper angle. 

 The supraspinal fossa is less than half the breadth of the infraspinal one ; and the upper 

 costa inclines at its fore part to near the spine, before it curves out again to the coracoid 

 (PI. XXI. figs. 12, 13, 52). The infraspinal fossa is made deep by the height of the 

 spine and the outbending of the lower border. The spine rises to a height of 5 lines 

 before expanding into the acromion, which attains a breadth of 4 lines, and is slightly 



