62 PROFESSOR OWEN ON THE AYE-AYE. 



The extensor digitorum communis (PI. XXIII. fig. 2,2?), arising, in common with the 

 extensor carpi radialis, from the ectocondyloid tubercle, accompanies that muscle in close 

 attachment therewith down half the forearm, then separates therefrom to allow the 

 abductor longus poUicis {ib. 25) to glide between them, and at about the same part of the 

 forearm itself divides into two fasciculi terminating in the extensor tendons. These pass 

 beneath the dorso-carpal ligament, beyond which they are connected together by strong 

 fasciae, forming, apparently, a broad band upon the metacarpus where the separate tendons 

 diverge to the second, third, fourth, and fifth digits. They expand as they pass over the 

 proximal joints, where they are connected with the divisions of the shorter extensor 

 tendons. A deep-seated extensor, forming almost a separate muscle, sends subsidiary 

 tendons (2? ") to the fourth and fifth digits, expanding upon the capsules of the proximo- 

 digital joints. In this respect Chiromys resembles Tarsius\and diflfers from Stenops, in 

 which, according to Vrolik^, the deep extensor of the fourth and fifth fingers is 

 wanting. 



The abductor longus pollicis (PI. XXIII. fig. 2, 25) arises from the lower part of the 

 ectocondyloid tuberosity, descends on the radial side of the extensor longus pollicis as far 

 as the middle of the antibrachium, then diverges obliquely radiad, decreasing in breadth 

 as it passes over the tendons of the two radio-carpal extensors, passes with them through 

 the dorso-carpal ligament, and goes to be inserted into the radial side of the metacarpal 

 of the poUex. 



The extensor longus pollicis (PI. XXIII. fig. 2, 37) arises from the upper third of the 

 ulna, passes down the back part of the interosseous space, becomes tendinous at the 

 lower third of the forearm, bends radiad beneath the index and medius tendons of the 

 common extensor, and, after passing through the dorso-carpal ligament, proceeds to 

 its insertion into the back part of the proximal phalanx of the thumb. 



Beneath the foregoing, arising from the middle of the ulna and interosseous ligament, 

 is a small muscle, answering to the ' indicator,' but dividing into two slender tendons, 

 which, after connexion with those of the superficial extensors, go respectively to the index 

 and medius digits, dividing upon the proximal phalanx, and uniting to be inserted into 

 the base of the distal phalanx. 



Some of the smaller muscles of the digits are indicated in the description of the Plates. 



The forearm of the Aye-aye appears to be incapable of being naturally brought into a 

 straight line with the humerus, but freely bends within the limits of the obtuse angle to 

 which it can, with moderate force, be stretched. 



The pronator teres (Pis. XXII. & XXIII. fig. 1 , 32) arises, in close connexion with the 

 palmaris longus, from the lower and fore part of the entocondyloid ridge, and is inserted 

 by a broad flat tendon into the radius at and above its middle part. The carneous 

 fibres continue on the outer part of the muscle to near its insertion. 



The flexor carpi radialis (i6. 31), with a similar but deeper origin, continues fleshy 

 ' Burmeister, op. eit. " Op. cit. p. 45. 



