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



Cleido-occipitalis. Origin on the clavicle just laterad of the sterno- 

 mastoid. Insertion by aponeurosis on the side of the occiput just laterad 

 of and in the same plane with the acromio-trapezius. On its outer sur- 

 face its relations are with the ceruico-auricularis; on its inner with the 

 rhomboideus, the atlanto-acromialis, and the cleido-mastoideus. 



Omo-deido-transversarius . This includes two distinct muscles as in 

 Didelphis, a dorsal part or "atlanto-scapularis" and a ventral part or 

 " atlanto-acromialis" The dorsal part has its origin on the side of the 

 body of the atlas immediately laterad of the origin of the ventral part. 

 The insertion is on the front of the scapular spine in its vertebral fourth 

 just ventrad of the insertion of the rhomboideus minor. It is a weaker 

 more slender muscle than the ventral part and does not widen so at its 

 insertion. The ventral part has origin on the side of the hypapophysial 

 tubercle of the atlas. Its insertion is broad from the caudal side of the 

 metacromion process of the scapula and for a short distance ventrad 

 along the deltoid fascia over the acromio-deltoid muscle where it sends 

 a few fibers ventrad. 



MUSCLES OF THE THORAX. 



Pectoralis minor. Origin from the sides of the fourth and fifth 

 sternebrae. Insertion on the lesser tuberosity of the humerus and the 

 deltoid ridge by a broad slightly tendinous aponeurosis much wider 

 than in Didelphis. Its outer surface has relation with the pectoralis 

 major, its inner with the rectus dbdominis, scalenus, etc. 



Pectoralis major. Origin from the median line of the entire sternum. 

 Insertion on the distal part of the inner edge of the deltoid ridge. Its 

 outer edge is curled under and near the insertion it has a slight aponeu- 

 rotic connection with the ociphihumeralis as in Didelphis. 



Supracostalis. Origin by broad aponeurosis from the second, third, 

 fourth and fifth sternebrae. Insertion fleshy on the side of the first rib. 

 This muscle, which Coues called " sterno-costalis" and others designate 

 transversus costarum, has practically the same relations as in Didelphis. 

 Its broad aponeurosis for its entire length covers the rectus abdominis. 



Subclavius. Arises from the first rib and inserts on the outer side of 

 the distal end of the clavicle, not extending to the scapular spine as in 

 Didelphis. In this it agrees with Phascologale, and some other Australian 

 forms (Macropus sp., Phalanger sp.). 



Serratus magnus. Origin posteriorly by six very distinct digitations 

 on the sides of the ribs from the third to the eighth inclusive. Anteriorly 

 there are no distinct digitations and the origin is from the joints of cos- 

 tal cartilages with the first, second and third ribs. Insertion on the pos- 



