40 FIELD MUSEUM OF NATURAL HISTORY ZOOLOGY, VOL. XIV. 



the front of the first caudal. The next tendon laterad runs to the 

 eleventh caudal, the next to the twelfth and so they continue to the 

 twentieth caudal. The muscle is broadly spindle shaped and occupies 

 the sacral basin, its two halves forming an elongate ellipse between the 

 two halves of the psoas magnus anteriorly and of the iliococcygeus 

 posteriorly. It consists of superposed laminae each becoming tendi- 

 nous before issuing from the pubis. 



MUSCLES OF THE ANTERIOR LIMB. 

 Plate V. 



Spino-deltoideus. Origin from the middle third of the scapular 

 spine. Insertion on the distal end and outer edge of the deltoid ridge of 

 the humerus. At its insertion it passes beneath and nearly at right angles 

 to the acromio-deltoideus. 



Acromio-deltoideus. Origin on the acromion and the proximal half 

 of the clavicle. Insertion on the inner end of the flattened surface of the 

 deltoid ridge opposite the insertion of the pectoralis major. It covers the 

 rather broad surface of the deltoid ridge and is a thicker muscle than in 

 Didelphis and more distinct from the spino-deltoideus and the pectoralis. 

 It is fan-shaped, the fibers from the clavicle and those from the acromion 

 converging toward a median raphe and coming to a point ventrally. 



Subscapularis. Origin from practically the whole of the expanded 

 ental surface of the scapula. Insertion by a short broad tendon on the 

 lesser tuberosity of the humerus. It is slightly thicker dorsally than 

 ventrally but in general is thin and flat. 



Supraspinatus. Origin from the surface of the supraspinous fossa. 

 It passes entad of the clavicle between the coracoid and the acromion 

 and inserts on the greater tuberosity of the humerus. It is about twice 

 as large as the infraspinatus and relatively larger than in Didelphis, 

 agreeing more nearly with Phalanger, Perameles, Phascologale, etc. 



Infraspinatus. Origin from the infraspinous fossa, including the 

 ental surface of the metacromion and acromion, the axillary border of 

 the scapula, and from a tendinous raphe between it and the proximal 

 part of the teres. Insertion partly fleshy and partly tendinous on the 

 greater tuberosity of the humerus. A weak aponeurosis from the 

 infraspinous fossa near the base of the acromion may represent the 

 teres minor, but it is very indefinite. A teres minor is reported for Chiro- 

 nectes (Sidebotham) but not for Didelphis. 



Epitrochlearis. Origin from the lower border of the latissimus slight- 

 ly (2 mm.) before it passes beneath the biceps. Insertion on the olecranon 

 process of the ulna. 



