74 PHYSIOLOGICAL SERIES. 



effects of the shock, or impulse, which the anterior ex- 

 tremities receive when the animal alights from a leap. 

 0. C. 255 K. 



B. 122. Right shoulder-joint of a Duck-billed Platypus ( OrnitJw- 

 rhynchus anatinus) . The glenoid cavity has the form of a 

 groove with open ends, deeply concave in a dorso-ventral 

 direction, but slightly convex transversely. The head of 

 the humerus is laterally expanded and constitutes a roller- 

 shaped condyle of slightly crescentic form ; the hollow of the 

 crescent fits against the lower (coracoid) lip of the glenoid 

 groove and is connected to it by a stout gleno-humeral 

 ligament. The form of the articular surfaces and looseness 

 of the capsule except where it forms the gleno-humeral liga- 

 ment allow of considerable rotation of the humerus. 



Attached to the apex of the internal tuberosity there is a 

 small loose nodule of bone on which the subscapularis muscle 

 is inserted. This bone has been compared to the os humero- 

 scapulare of the bird. 



B. 123. Right shoulder-joint of an Opossum (JDidelphys marsu- 

 pialis). The capsule has been opened to expose a stout 

 gleno-humeral ligament, which arises from the glenoid 

 border beneath the biceps tendon, passes diagonally across 

 the joint-cavity free of the capsule, and is attached to the 

 inner side of the head of the humerus. The gleno-humeral 

 ligament in this and the following specimens is apparently 

 the middle gleno-humeral ligament of human anatomy. 



B. 124. Left shoulder-joint of a Tasmanian Devil (Sarcopliilas 

 \_Dasyurus~\ ur sinus) showing a similar gleno - humeral 

 ligament. 



B. 125. Left shoulder of a Six-banded Armadillo (Dasypus 

 sexcinctus). A blue glass rod has been placed beneath the 

 gleno-humeral ligament that is free in the joint-cavity. 

 A green glass has been passed beneath a special thickening 

 of the external wall of the capsule. 



B. 126. Right shoulder-joint of Nine-banded Armadillo (Tatusia 

 novemcincta) . A bristle has been passed below the free 

 gleno-humeral ligament 



