MAY, 1921. AMERICAN MARSUPIAL, C^NOLESTES OSGOOD. 41 



Teres major. Origin from the posterior ventral angle of the scapula 

 in close relation with the subscapularis. Insertion on the bicipital groove 

 slightly proximad of and in conjunction with that of the latissimus. 



Coracobrachialis brevis. Origin on the coracoid process entad of the 

 biceps. Insertion on the humerus just proximad of the insertion of the 

 teres. It is very slightly developed, almost rudimentary, and in its 

 fleshy part consists of a very thin layer of fibers instead of a thick belly 

 as in Didelphis. In one specimen it appeared to insert in the tissue of the 

 medial head of the triceps rather than on the humerus. 



Biceps brachii. Origin by a single tendon from the coracoid process 

 of the scapula and adjacent fascia. Soon after becoming fleshy it is 

 readily divisible into two distinct muscles which run in close apposition 

 to pass into the forearm between the pronator teres and the extensor 

 carpi radialis brevis. The outer muscle inserts by a narrow flat tendon 

 on the tubercle of the radius. The inner muscle is partially attached to 

 the brachialis near its insertion and then its tendons divide and pass on 

 either side of the tendon of the brachialis to insertions on the side of the 

 ulna distad of the lesser sigmoid cavity. In some of the Macropodidae 

 the biceps is completely divided but in some other diprotodonts and in 

 polyprotodonts generally its relations are reported essentially as above. 



Brachialis anticus. Origin from the lesser tuberosity and the border 

 of the head of the humerus passing around the middle of the front of the 

 humerus and thence distad. At about the middle of the front of the 

 humerus it becomes attached to the bone; between this and its origin 

 it is free or nearly so. Thence it continues along the humerus to the elbow 

 joint where it twists further and has final insertion just distad of the 

 lesser sigmoid cavity on the inner surface of the ulna by a flattened ten- 

 don which passes between the divided tendons of the biceps. 



Triceps brachii. The long head has its origin as usual on the axillary 

 border of the scapula just dorsad of the glenoid cavity. Its insertion by 

 common tendon with the lateral head is on the outer angle of the 

 olecranon process of the ulna. 



The lateral head arises beneath the posterior border of the head of 

 the humerus and thence is free from the humerus to its union with the 

 long head. Its posterior aspect is hollowed to receive the long head for 

 most of its length and the two are fairly distinct. The median head 

 arises from the posterior aspect of the humerus for practically its entire 

 length, reaching dorsally within 2 mm. of the lesser tuberosity and 

 thence to the olecranon fossa. Its insertion is on the inner angle of the 

 olecranon process of the ulna quite distinct from that of the other two 

 heads. 



The triceps of Canolestes is characterized by the distinctness of the 



