140 ANATOMY OF THE WOOD RAT 



medial connection with the remainder of the scapula, and 

 the termination of its juncture with the latter constitutes 

 the spinal notch. 



The subscapularis arises from almost the entire medial 

 surface of the scapula. The plane of the latter is interrupted 

 by the subscapular ridge, the definition of which varies 

 individually, and the subspinal fossa. Upon either side of 

 the former arises one of the two main divisions of the sub- 

 scapular muscle. The form of the subspinal fossa is appar- 

 ently a mechanical result of the presence of the spine upon 

 the lateral surface. The insertion of the rhomboideus 

 anticus exhibits a tendency to follow the subspinal fossa for 

 a short distance along its dorsal termination. This same in- 

 sertion, together with that of the rhomboideus posticus 

 situated more dorsad, extends along the vertebral border of 

 the scapula for a short distance. Upon the medial border 

 of the glenovertebral angle are inserted the levator scapulae 

 and serratus magnus, and a small portion of the teres major 

 also takes origin from this surface. The rate of ossification 

 of the border of the scapula at the glenovertebral angle is 

 slow, and this line of ossification, of variable extent, remains 

 most clearly visible in Teonoma. Any variation in the re- 

 mainder of this portion of the scapula is individual, however, 

 rather than subgeneric. 



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The triceps longus originates upoii the ventral third of the 

 axillary border of the medial scapula. From the constricted 

 neck, the slightly enlarged head of the scapula extends 

 cranio-ventrad. Upon this is the glenoid cavity, articulating 

 with the humerus, and ventro-caudad, the caudal process of 

 the head. It is best developed in Teonoma, due probably to 

 the larger head of the humerus in that animal. Upon the 

 dorso-cranial border of the head is the coracoid process, 

 rather slender and inclined first mediad and then ventrad. 

 Upon its tip originate the coracobrachialis and biceps brevis, 

 and from its base, the biceps longus. This, too, is best 



