FORE-LIMB. 127 



ulna. (3) The short head arises from the humerus on a 

 level with the pectoralis insertion, and is inserted on the 

 radius. The flexion of the elbow is probably to a great 

 extent helped by the supinator longus and pronator teres. 

 The former muscle is in two parts, and arises from the 

 whole length of the humerus distal to the deltoid. The 

 flexor digitorum has a common belly which gives off a 

 powerful tendon to each of the digits. 



Windle & Parsons, Proc. Zool. Soc. 1899, p. 314. 



C. 147. Muscles of the left fore-limb of a Manatee (Tricheehus 

 manatns). Locomotion is entirely due to the powerful 

 spatulate tail, the fore-limbs being mainly used for balan- 

 cing and steering, and also to a limited extent for clasping 

 the seaweed when browsing. The muscles, besides showing 

 many peculiarities in detail, are remarkable for the great 

 development of those connected with the fingers. In con- 

 sequence the hand has greater freedom of movement than 

 its external appearance would suggest, and affords in this 

 particular a striking contrast to the flipper of the Cetacea. 

 The following muscles should be noticed : The cephalo- 

 humeral (cleido-occipitalis) , originating from the occiput 

 and inserted on the humerus between the deltoid and 

 pectoralis major (its insertion only is shown). The biceps 

 is in a much reduced condition ; it consists of two separate 

 heads one of fair size rising from the coracoid and inserted 

 halfway down the inner side of the humerus, and a smaller 

 long head rising from the. glenoid border and inserted 

 partly upon the humerus near the short-head insertion, and 

 partly by a fine tendon upon the radius. The brachialis 

 internus is of great size, and seems to have more or less 

 usurped the function of the biceps. The tendons of the 

 extensor digitorum communis branch out at the wrist at a 

 wide angle, and when in action would strongly adduct 

 the digits. The supinator longus is attached to the carpus 

 (a common insertion among Marsupials). Only one ex- 

 tensor carpi radialis is present. The pronator teres is fused 

 with the flexor carpi radialis. This composite muscle and 

 the flexor sublimis pass very obliquely across the fore- 

 arm, and doubtless have a strong pronating action. Tho 



