284 



AN INTRODUCTION TO ZOOLOGY 



only the clavicle which is a membrane bone, but in addition there 

 are also developed in certain of the tendons, sesamoid bones. 



Pectoral Girdle. 



Compared with Rana we find the pectoral girdle much 

 reduced and consisting mainly of two elements, a dorsal and a 



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ventral. The scapula, or shoulder blade, is a thin flat triangular 

 plate of bone. The apex of the triangle bearing the glenoid facet, 

 lies laterally over the first rib and the remainder passes back dorsally 



