M.MHi'S'TOfi'H — Muscular Anatomy of Choloejms didactylus. 71 



Supraspinatus, infraspinatus, and siibscapularis presented no fea- 

 tures of interest, except that the weight of the latter equalled the com- 

 bined weights of the two former ; a nearly similar condition occurred 

 in Arctopithecus. 



Subscapulohumeralis was very long and quite distinct. 



Serratas magnus, which had no separate levator scapulae portion, 

 arose from the upper six and from the eighth ribs, as well as from the 

 three lower cervical transverse processes, and was inserted into the 

 scapula, as usual. 



Biceps humeralis is a curious muscle, but by no means so complex 

 as in Arctopithecus. It has a simple, long tendon of origin from the 

 scapula, which expands into two bellies, the superior of which joins 

 the acromial deltoid, and is inserted into the tubercle of the radius, as 

 usual; the deeper segment is inserted into the coronoid process of the 

 ulna, along with, and inseparable from, brachialis anticus, which arises 

 from the outer aspect of the humerus extei-nal to the insertion of the 

 deltoid, and extending half-way up the bone. This arrangement 

 appears to present us with another variety in the already numerous 

 modifications of attachment of biceps in the Edentata. 



Dorso-epitrochlearis (Tricipiti accessorius) is a large muscle arising, 

 as usual, from triceps, and inserted entirely into the supracondyloid 

 process. Mr. Gralton describes it as being thin, cylindrical, rolled on 

 itself, and inserted chiefly into the anterior ridge of the supracondyloid 

 foramen, but slightly into the humerus above the foramen and below 

 the insertion of coracobrachialis ; there was no forearm prolongation. 



Triceps longus, externus, and internus, are all normal, their heads 

 being more or less fused. 



Anconeus externus is small, and can only be artificially separated 

 from triceps longus, and anconeus internus (epitrocles- anconeus) is 

 in the same condition with regard to its insertion, though quite dis- 

 tinct at the origin. It was present in Mr. Galton's specimen, but is 

 not described. 



Pronator radii teres had a similar origin in our specimen and in 

 Professor Humphry's, viz., above the internal condyle of the humerus, 

 but the insertions differed considerably. Professor Humphry found it 

 to be attached to the lower end of the radius opposite to the insertion 

 of supinator longus, whereas, in our specimen it fused with the lower 

 part of that muscle, which consists of two parts — a superficial which 

 arises from the deltoid, but is distinguished from it by a tendinous 

 inscription, and was inserted into the fascia of the front of the wrist, 

 and a deep segment which is enormously developed, arising from the 

 humerus outside the musculospiral ridge and extending as far down as 

 the condyle, and inserted into the radius for the lower four- fifths of its 

 length. Professor Humphry's specimen resembled ours in being 

 double, in the insertion of the superficial portion, and the origin of the 

 deeper ; he describes the origin of the former part as being high up on 

 the humerus, not from the deltoid, whilst the insertion of the deeper seg- 

 ment was into the end of the radius, much as in man ; this arrange- 



