and structure it is much like the episternum, 

 except that it is larger and deeply notched at 

 its caudal margin. The omosternum is an 

 elongate bone narrowed at its middle and 

 broadened at either end. Its cephalic ex- 

 tremity is articulated with the epistemum. 

 The sternum proper is attached to and 

 extends cephalad from the xiphistemtim. 

 This bone is narrow in its middle, gradually 

 broadening towai'ds either end. Between 

 the omosternum. and the sternum extends a 

 cartilage known as the epicoracoid cartilage. 

 In old individuals, this is almost concealed by 

 the mesal development of the clavicles and 

 coracoids. 

 (b). The lateral portions or wings — ^The suprasca- 

 pula is the most distal (dorsal when the 

 girdle is in situ) element, and is trapezoidal in 

 shape. The distal portion is composed of 

 hyaline cartilage, whUe the proximal or mesal 

 half is composed of bone. The scapula is 

 articulated with the proximal end of the 

 suprascapula. It is a fiat, compact bone, con- 

 tracted in the middle and wider at the ends. 

 Mesally it is articulated with the clavicle and 

 coracoid. Between the scapula and epi- 

 coracoid cartilage are two bones; the more 

 cephalic is the clavicle, which is very narrow; 

 the caudal one is the coracoid, contracted in 

 the middle and very broad at its mesal end 

 where it articulates with the epicoracoid 

 cartilage. At its distal extremity it takes 

 part with the scapula in forming the glenoid 

 cavity for the articulation of the arm-bone 

 (humerus). 



Make an enlarged drawing of the ventral aspect, 

 with the notched xiphistemum directed 

 toward the bottom of the sheet. 



(i8). The shoulder girdle of the common toad. This illus- 

 trates the type of girdle found among the Arcifera. 

 i6 



